<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:7c032ae5-644a-4945-8a55-5d03f1d368ab,g:17b5af2a-b23c-4c95-8d0b-b4d33ac3b655-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://pwp.com/role/Cover" xlink:type="simple" xlink:href="pwp-20240630.xsd#Cover"/>
  <link:definitionLink xlink:role="http://pwp.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_659391f4-a6c8-43f9-86b9-566055222815" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_DocumentInformationTable_659391f4-a6c8-43f9-86b9-566055222815" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_f2fef24d-2e1c-4510-9ed3-6f20f5b4d180" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_659391f4-a6c8-43f9-86b9-566055222815" xlink:to="loc_us-gaap_StatementClassOfStockAxis_f2fef24d-2e1c-4510-9ed3-6f20f5b4d180" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f2fef24d-2e1c-4510-9ed3-6f20f5b4d180_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f2fef24d-2e1c-4510-9ed3-6f20f5b4d180" xlink:to="loc_us-gaap_ClassOfStockDomain_f2fef24d-2e1c-4510-9ed3-6f20f5b4d180_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_468c31fe-3f63-4cd5-a6c1-47694924aa8f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f2fef24d-2e1c-4510-9ed3-6f20f5b4d180" xlink:to="loc_us-gaap_ClassOfStockDomain_468c31fe-3f63-4cd5-a6c1-47694924aa8f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_ca74c9ea-a4a7-42fe-b4f0-2b2a32fa5a85" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_468c31fe-3f63-4cd5-a6c1-47694924aa8f" xlink:to="loc_us-gaap_CommonClassAMember_ca74c9ea-a4a7-42fe-b4f0-2b2a32fa5a85" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_f55dfafc-f7f4-4d85-88d5-e0c28d6f7247" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_468c31fe-3f63-4cd5-a6c1-47694924aa8f" xlink:to="loc_us-gaap_CommonClassBMember_f55dfafc-f7f4-4d85-88d5-e0c28d6f7247" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_e5ca3d9e-e465-4741-aee7-217713c2c518" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_DocumentType_e5ca3d9e-e465-4741-aee7-217713c2c518" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_98a46ea7-92ae-4b65-9c10-92f757601ee3" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_DocumentQuarterlyReport_98a46ea7-92ae-4b65-9c10-92f757601ee3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_44a000cb-fcc6-4e69-88df-9ac41daa6279" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_DocumentPeriodEndDate_44a000cb-fcc6-4e69-88df-9ac41daa6279" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_e4c7a256-3583-4dff-a075-362b58fe04bc" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_DocumentTransitionReport_e4c7a256-3583-4dff-a075-362b58fe04bc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_e0dc1945-75e8-49c7-9dc0-0ac93c243d29" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityFileNumber_e0dc1945-75e8-49c7-9dc0-0ac93c243d29" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_2d0aa06e-48ed-4866-b372-1f84a88697b9" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityRegistrantName_2d0aa06e-48ed-4866-b372-1f84a88697b9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_6717e243-45b8-4827-a567-dac959b135bb" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityIncorporationStateCountryCode_6717e243-45b8-4827-a567-dac959b135bb" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_bdbe99b6-4e07-40ff-b172-f8953f4f35af" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityTaxIdentificationNumber_bdbe99b6-4e07-40ff-b172-f8953f4f35af" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_b7d8ce4a-8a5c-4a60-af64-5892d71acfa8" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityAddressAddressLine1_b7d8ce4a-8a5c-4a60-af64-5892d71acfa8" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_ffb0759a-396e-4622-a78b-bfc96a15641d" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityAddressCityOrTown_ffb0759a-396e-4622-a78b-bfc96a15641d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_70ef0c06-737d-48f9-9ec8-33dbe88bbd95" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityAddressStateOrProvince_70ef0c06-737d-48f9-9ec8-33dbe88bbd95" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_74a2e29f-49a7-4df1-98ec-7363d8d0eccc" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityAddressPostalZipCode_74a2e29f-49a7-4df1-98ec-7363d8d0eccc" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_922aa921-4010-4b97-8439-a36e84fa743f" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_CityAreaCode_922aa921-4010-4b97-8439-a36e84fa743f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_14bdac7f-b1cd-4b0e-8d8c-52462cb7a852" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_LocalPhoneNumber_14bdac7f-b1cd-4b0e-8d8c-52462cb7a852" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_aaf61332-7e7d-41ce-864f-3b33fc62ba19" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_Security12bTitle_aaf61332-7e7d-41ce-864f-3b33fc62ba19" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_ff5d7dcb-0bb2-4dd7-90fa-06c8015deaf8" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_TradingSymbol_ff5d7dcb-0bb2-4dd7-90fa-06c8015deaf8" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_1ecf94e0-0e07-4e04-9ee5-01ff496d2d1a" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_SecurityExchangeName_1ecf94e0-0e07-4e04-9ee5-01ff496d2d1a" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_a63eafee-5c58-4c0d-b013-651de52b7980" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityCurrentReportingStatus_a63eafee-5c58-4c0d-b013-651de52b7980" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_5a0db457-b12b-43ee-b71f-b1d1b5c34805" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityInteractiveDataCurrent_5a0db457-b12b-43ee-b71f-b1d1b5c34805" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_ba305661-cb32-495b-b793-a0609dfe7833" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityFilerCategory_ba305661-cb32-495b-b793-a0609dfe7833" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_bd2d3ae6-7984-47ff-85a6-70d9198452f2" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntitySmallBusiness_bd2d3ae6-7984-47ff-85a6-70d9198452f2" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_ee6d769a-5ee2-457b-ba1c-43c48807ff5c" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityEmergingGrowthCompany_ee6d769a-5ee2-457b-ba1c-43c48807ff5c" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityExTransitionPeriod_a8a46607-346b-4889-aeb8-733289da0acd" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityExTransitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityExTransitionPeriod_a8a46607-346b-4889-aeb8-733289da0acd" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_0ceb6dd0-f6da-4b9b-bb14-a96455dbb67e" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityShellCompany_0ceb6dd0-f6da-4b9b-bb14-a96455dbb67e" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_9c2afb14-e1f7-4fd5-b61b-a983b7f99a35" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_9c2afb14-e1f7-4fd5-b61b-a983b7f99a35" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_3d6a113f-a7bd-4374-96f6-b0dcdedcfe5d" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_EntityCentralIndexKey_3d6a113f-a7bd-4374-96f6-b0dcdedcfe5d" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_4d81f6e8-aa38-423a-a06f-cd94baecd3b2" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_CurrentFiscalYearEndDate_4d81f6e8-aa38-423a-a06f-cd94baecd3b2" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_83136896-1200-4a15-8049-998b95a0bd6c" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_DocumentFiscalYearFocus_83136896-1200-4a15-8049-998b95a0bd6c" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_60f60670-5f8f-4943-9217-b67b96901fe0" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_DocumentFiscalPeriodFocus_60f60670-5f8f-4943-9217-b67b96901fe0" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_1ab277b8-3f28-482e-8383-fa9a869b29c1" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_16ee048c-8c2a-46ec-94b9-3db80871223b" xlink:to="loc_dei_AmendmentFlag_1ab277b8-3f28-482e-8383-fa9a869b29c1" xlink:type="arc" order="29"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/CondensedConsolidatedStatementsofFinancialConditionUnaudited" xlink:type="simple" xlink:href="pwp-20240630.xsd#CondensedConsolidatedStatementsofFinancialConditionUnaudited"/>
  <link:definitionLink xlink:role="http://pwp.com/role/CondensedConsolidatedStatementsofFinancialConditionUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_344bbdff-9285-4fd9-992e-d6636255d447" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_dd7db4b8-d274-4e4a-bcff-08fd06a8d062" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_344bbdff-9285-4fd9-992e-d6636255d447" xlink:to="loc_us-gaap_StatementTable_dd7db4b8-d274-4e4a-bcff-08fd06a8d062" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_459c8a6b-2049-4a35-a3f7-a9284bc838a4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_dd7db4b8-d274-4e4a-bcff-08fd06a8d062" xlink:to="loc_us-gaap_StatementClassOfStockAxis_459c8a6b-2049-4a35-a3f7-a9284bc838a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_459c8a6b-2049-4a35-a3f7-a9284bc838a4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_459c8a6b-2049-4a35-a3f7-a9284bc838a4" xlink:to="loc_us-gaap_ClassOfStockDomain_459c8a6b-2049-4a35-a3f7-a9284bc838a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_2ba31108-1c7f-4f29-ae66-5b33a4ff9c13" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_459c8a6b-2049-4a35-a3f7-a9284bc838a4" xlink:to="loc_us-gaap_ClassOfStockDomain_2ba31108-1c7f-4f29-ae66-5b33a4ff9c13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_1b545568-c4d4-4329-b8d5-0f140f4586f4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_2ba31108-1c7f-4f29-ae66-5b33a4ff9c13" xlink:to="loc_us-gaap_CommonClassAMember_1b545568-c4d4-4329-b8d5-0f140f4586f4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_fe964555-9a64-4c72-a5f5-3acfe28c9446" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_2ba31108-1c7f-4f29-ae66-5b33a4ff9c13" xlink:to="loc_us-gaap_CommonClassBMember_fe964555-9a64-4c72-a5f5-3acfe28c9446" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_bd7a0e24-9cab-4fbd-afc1-8b9b02cde4af" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_dd7db4b8-d274-4e4a-bcff-08fd06a8d062" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_bd7a0e24-9cab-4fbd-afc1-8b9b02cde4af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_bd7a0e24-9cab-4fbd-afc1-8b9b02cde4af_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_bd7a0e24-9cab-4fbd-afc1-8b9b02cde4af" xlink:to="loc_us-gaap_RelatedPartyDomain_bd7a0e24-9cab-4fbd-afc1-8b9b02cde4af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_a70e1c80-63b7-43df-829c-4dfe10715bb7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_bd7a0e24-9cab-4fbd-afc1-8b9b02cde4af" xlink:to="loc_us-gaap_RelatedPartyDomain_a70e1c80-63b7-43df-829c-4dfe10715bb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_0f5e529d-4e9a-4104-ba9f-e9fed06f31e5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_a70e1c80-63b7-43df-829c-4dfe10715bb7" xlink:to="loc_us-gaap_RelatedPartyMember_0f5e529d-4e9a-4104-ba9f-e9fed06f31e5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_344bbdff-9285-4fd9-992e-d6636255d447" xlink:to="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_a3d54b67-0c42-47cf-a03f-c5da40cc6a92" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_a3d54b67-0c42-47cf-a03f-c5da40cc6a92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_6d87bbeb-07a6-431e-9456-ad66fdc55d8d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_RestrictedCash_6d87bbeb-07a6-431e-9456-ad66fdc55d8d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestments_dc28c837-2a2e-4bfe-879a-31cf6f352629" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_ShortTermInvestments_dc28c837-2a2e-4bfe-879a-31cf6f352629" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_56fd18a8-bb1f-433a-84b5-b065ecc04167" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_AccountsReceivableNet_56fd18a8-bb1f-433a-84b5-b065ecc04167" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivablesNetCurrent_b357a1d0-e724-49c4-b908-9835a1f8bfc3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherReceivablesNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_OtherReceivablesNetCurrent_b357a1d0-e724-49c4-b908-9835a1f8bfc3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_5e13ae43-f006-4a44-b164-698e798b5fda" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_5e13ae43-f006-4a44-b164-698e798b5fda" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_0a4da014-ea92-48b9-81c9-a5e2f166159e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_0a4da014-ea92-48b9-81c9-a5e2f166159e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_96d78f7a-f0f3-4240-b355-bc6114a25a7d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_Goodwill_96d78f7a-f0f3-4240-b355-bc6114a25a7d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssets_38baf8d7-9b8c-4ffa-8023-36d824b4a3e6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PrepaidExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssets_38baf8d7-9b8c-4ffa-8023-36d824b4a3e6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_2146c2f8-0d7c-49e6-baab-9ed81cce91ee" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_2146c2f8-0d7c-49e6-baab-9ed81cce91ee" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_a52c96cf-364d-4487-b38c-f3437f5feccc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_a52c96cf-364d-4487-b38c-f3437f5feccc" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_9be12700-d20a-4809-a221-bc0ea2a2e208" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a1bfb5e0-ee28-423b-9651-1c5ae2104b26" xlink:to="loc_us-gaap_Assets_9be12700-d20a-4809-a221-bc0ea2a2e208" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_41701873-5572-4737-a369-34dcfd2d9675" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_344bbdff-9285-4fd9-992e-d6636255d447" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_41701873-5572-4737-a369-34dcfd2d9675" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent_4d9090c0-43ef-463e-a60f-79e9a5b43502" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_41701873-5572-4737-a369-34dcfd2d9675" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent_4d9090c0-43ef-463e-a60f-79e9a5b43502" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_ab92998d-0ed7-4ab7-97b4-9fe5cb8eee07" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_41701873-5572-4737-a369-34dcfd2d9675" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_ab92998d-0ed7-4ab7-97b4-9fe5cb8eee07" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_0a6c509d-de5e-4a34-b29e-0afcb73bf621" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_41701873-5572-4737-a369-34dcfd2d9675" xlink:to="loc_us-gaap_OperatingLeaseLiability_0a6c509d-de5e-4a34-b29e-0afcb73bf621" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_AmountDuePursuantToTaxReceivableAgreement_b168ae7b-589a-4ba6-80ee-041b0eb60557" xlink:href="pwp-20240630.xsd#pwp_AmountDuePursuantToTaxReceivableAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_41701873-5572-4737-a369-34dcfd2d9675" xlink:to="loc_pwp_AmountDuePursuantToTaxReceivableAgreement_b168ae7b-589a-4ba6-80ee-041b0eb60557" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_c53f2187-3a4a-4f07-946b-9a299c29c6fb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_41701873-5572-4737-a369-34dcfd2d9675" xlink:to="loc_us-gaap_Liabilities_c53f2187-3a4a-4f07-946b-9a299c29c6fb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_a3b80692-c839-46cf-a4e8-1f6e25633427" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_41701873-5572-4737-a369-34dcfd2d9675" xlink:to="loc_us-gaap_CommitmentsAndContingencies_a3b80692-c839-46cf-a4e8-1f6e25633427" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_8f98fd23-cf4c-492b-86c7-3fcc002f7c6a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_41701873-5572-4737-a369-34dcfd2d9675" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_8f98fd23-cf4c-492b-86c7-3fcc002f7c6a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_344bbdff-9285-4fd9-992e-d6636255d447" xlink:to="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_bbbe13d6-8b8a-46c9-9d0c-ec5a221d4885" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:to="loc_us-gaap_CommonStockValue_bbbe13d6-8b8a-46c9-9d0c-ec5a221d4885" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_c168d83f-7a43-4393-b139-37e5ffa41950" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:to="loc_us-gaap_PreferredStockValue_c168d83f-7a43-4393-b139-37e5ffa41950" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_64782f2c-cfc5-41d2-aff1-fc9050f4783a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_64782f2c-cfc5-41d2-aff1-fc9050f4783a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_18915827-e197-4fd6-9ae0-1b9d67211fb5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_18915827-e197-4fd6-9ae0-1b9d67211fb5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_a09e4154-82ed-4207-9723-f69ba911cd4e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_a09e4154-82ed-4207-9723-f69ba911cd4e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonValue_57fb787c-a5a9-427b-8fd7-7f7cb193ce7b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:to="loc_us-gaap_TreasuryStockCommonValue_57fb787c-a5a9-427b-8fd7-7f7cb193ce7b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_4340e1cd-2643-40a8-9d30-d755495b0e49" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:to="loc_us-gaap_StockholdersEquity_4340e1cd-2643-40a8-9d30-d755495b0e49" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_680f9a54-8b01-4209-a5cf-97f08b797e95" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MinorityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:to="loc_us-gaap_MinorityInterest_680f9a54-8b01-4209-a5cf-97f08b797e95" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_b6dafb03-ef07-419e-bd84-7d39a20787b3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_b6dafb03-ef07-419e-bd84-7d39a20787b3" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_b1acc514-5746-427b-aad6-50eb9a71fbb0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_b8b08e53-64fd-48d0-8021-52e92eeb3847" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_b1acc514-5746-427b-aad6-50eb9a71fbb0" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/CondensedConsolidatedStatementsofFinancialConditionUnauditedParenthetical" xlink:type="simple" xlink:href="pwp-20240630.xsd#CondensedConsolidatedStatementsofFinancialConditionUnauditedParenthetical"/>
  <link:definitionLink xlink:role="http://pwp.com/role/CondensedConsolidatedStatementsofFinancialConditionUnauditedParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_a43703ff-bd5c-42c8-8d10-7bf74dec91f0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_StatementTable_a43703ff-bd5c-42c8-8d10-7bf74dec91f0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_deb6b4bd-c2ae-4d60-97aa-a375cd100271" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_a43703ff-bd5c-42c8-8d10-7bf74dec91f0" xlink:to="loc_us-gaap_StatementClassOfStockAxis_deb6b4bd-c2ae-4d60-97aa-a375cd100271" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_deb6b4bd-c2ae-4d60-97aa-a375cd100271_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_deb6b4bd-c2ae-4d60-97aa-a375cd100271" xlink:to="loc_us-gaap_ClassOfStockDomain_deb6b4bd-c2ae-4d60-97aa-a375cd100271_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_8478fd43-78c5-4431-a848-b8dc8096d1a1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_deb6b4bd-c2ae-4d60-97aa-a375cd100271" xlink:to="loc_us-gaap_ClassOfStockDomain_8478fd43-78c5-4431-a848-b8dc8096d1a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_9cf719c9-3e04-43d7-8ede-ae49d35b451e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_8478fd43-78c5-4431-a848-b8dc8096d1a1" xlink:to="loc_us-gaap_CommonClassAMember_9cf719c9-3e04-43d7-8ede-ae49d35b451e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_e26fcf83-94d0-400c-a0b7-6e1cc527fc2c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_8478fd43-78c5-4431-a848-b8dc8096d1a1" xlink:to="loc_us-gaap_CommonClassBMember_e26fcf83-94d0-400c-a0b7-6e1cc527fc2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquitySharesOutstanding_3a5cf81c-7cab-43d2-8302-3cdbfa824f70" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquitySharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_TemporaryEquitySharesOutstanding_3a5cf81c-7cab-43d2-8302-3cdbfa824f70" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityRedemptionPricePerShare_5612d076-b863-4a68-9221-063aaf87a90e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityRedemptionPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_TemporaryEquityRedemptionPricePerShare_5612d076-b863-4a68-9221-063aaf87a90e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivableAfterAllowanceForCreditLossCurrentRelatedPartyTypeExtensibleEnumeration_b9f2cac5-19a4-4f4a-90db-2b99f5aed939" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherReceivableAfterAllowanceForCreditLossCurrentRelatedPartyTypeExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_OtherReceivableAfterAllowanceForCreditLossCurrentRelatedPartyTypeExtensibleEnumeration_b9f2cac5-19a4-4f4a-90db-2b99f5aed939" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_436afa4d-da88-43f5-8210-bb93b16a3b01" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_436afa4d-da88-43f5-8210-bb93b16a3b01" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_6d922d91-31ba-482b-a97f-e571b741a577" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_6d922d91-31ba-482b-a97f-e571b741a577" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_45724daa-8e82-47e7-8966-7792147bcb3a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_CommonStockSharesIssued_45724daa-8e82-47e7-8966-7792147bcb3a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_8bf717a7-f862-4433-80e0-49ca45254264" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_8bf717a7-f862-4433-80e0-49ca45254264" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_0bb3c42f-157e-4f71-9892-00d5e8c50c9f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_0bb3c42f-157e-4f71-9892-00d5e8c50c9f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_59bfc212-641a-4de6-ae7d-dcc67541abd2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_59bfc212-641a-4de6-ae7d-dcc67541abd2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_fad6b1f0-c778-44a9-a9cb-f43e59f12042" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_fad6b1f0-c778-44a9-a9cb-f43e59f12042" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_af00b412-47d9-491e-a18a-7ed38030f42f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_PreferredStockSharesIssued_af00b412-47d9-491e-a18a-7ed38030f42f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_3b05c01e-c03c-4711-a40c-488d67e7ba6a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f41eee93-c4a2-4a08-8346-297b7646c9df" xlink:to="loc_us-gaap_TreasuryStockCommonShares_3b05c01e-c03c-4711-a40c-488d67e7ba6a" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/CondensedConsolidatedStatementsofOperationsUnaudited" xlink:type="simple" xlink:href="pwp-20240630.xsd#CondensedConsolidatedStatementsofOperationsUnaudited"/>
  <link:definitionLink xlink:role="http://pwp.com/role/CondensedConsolidatedStatementsofOperationsUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_4776979e-1cc4-4f51-ba4a-362dc8da6db3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_StatementTable_4776979e-1cc4-4f51-ba4a-362dc8da6db3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_05b00cd8-0013-4de9-a6aa-d7a4f003b975" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_4776979e-1cc4-4f51-ba4a-362dc8da6db3" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_05b00cd8-0013-4de9-a6aa-d7a4f003b975" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_05b00cd8-0013-4de9-a6aa-d7a4f003b975_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_05b00cd8-0013-4de9-a6aa-d7a4f003b975" xlink:to="loc_us-gaap_RelatedPartyDomain_05b00cd8-0013-4de9-a6aa-d7a4f003b975_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_b72cdb48-f58b-4fe3-8f1f-9ba0afa91434" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_05b00cd8-0013-4de9-a6aa-d7a4f003b975" xlink:to="loc_us-gaap_RelatedPartyDomain_b72cdb48-f58b-4fe3-8f1f-9ba0afa91434" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_2e434cab-e6d9-4937-9aea-65784c6894de" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_b72cdb48-f58b-4fe3-8f1f-9ba0afa91434" xlink:to="loc_us-gaap_RelatedPartyMember_2e434cab-e6d9-4937-9aea-65784c6894de" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_1c6557b9-8a3f-4e66-a38f-6201fcba17e7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_b72cdb48-f58b-4fe3-8f1f-9ba0afa91434" xlink:to="loc_us-gaap_NonrelatedPartyMember_1c6557b9-8a3f-4e66-a38f-6201fcba17e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_364fdc49-c8e7-4e30-acb1-e2df3a475a1e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_364fdc49-c8e7-4e30-acb1-e2df3a475a1e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_CompensationExpenseExcludingEquityBasedCompensation_00fc1b26-b349-4d8c-82bd-ad4ec0d62b60" xlink:href="pwp-20240630.xsd#pwp_CompensationExpenseExcludingEquityBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:to="loc_pwp_CompensationExpenseExcludingEquityBasedCompensation_00fc1b26-b349-4d8c-82bd-ad4ec0d62b60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_557fbf49-fde0-4788-9a17-84570c560d2e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_557fbf49-fde0-4788-9a17-84570c560d2e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_1e74778e-de62-42a8-a1bf-6e019ae8f451" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:to="loc_us-gaap_LaborAndRelatedExpense_1e74778e-de62-42a8-a1bf-6e019ae8f451" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_e99b67f1-71f8-4c05-9af4-6f0ee45da0bd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:to="loc_us-gaap_ProfessionalFees_e99b67f1-71f8-4c05-9af4-6f0ee45da0bd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommunicationsAndInformationTechnology_0e19b859-5e3d-4a47-8827-963deefa8d57" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommunicationsAndInformationTechnology"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:to="loc_us-gaap_CommunicationsAndInformationTechnology_0e19b859-5e3d-4a47-8827-963deefa8d57" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OccupancyNet_27f540a2-158c-4e49-ba7e-5e8747035a4f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OccupancyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:to="loc_us-gaap_OccupancyNet_27f540a2-158c-4e49-ba7e-5e8747035a4f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TravelAndEntertainmentExpense_1df24a1c-bb3f-43a4-81bb-c0b40d529623" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TravelAndEntertainmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:to="loc_us-gaap_TravelAndEntertainmentExpense_1df24a1c-bb3f-43a4-81bb-c0b40d529623" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_43795bf6-a034-4ccd-92d4-dcc57cd1d194" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_43795bf6-a034-4ccd-92d4-dcc57cd1d194" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_ea8d5cba-830f-4143-a0ab-e6403eb5f49c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:to="loc_us-gaap_DepreciationAndAmortization_ea8d5cba-830f-4143-a0ab-e6403eb5f49c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_004e9abe-6bce-401a-a6fa-c84334a9a6b6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_8143ce6b-0fff-4005-b261-ea70208ade20" xlink:to="loc_us-gaap_OperatingExpenses_004e9abe-6bce-401a-a6fa-c84334a9a6b6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_54da92d9-5227-465b-a60e-9ba5e675f6bc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_OperatingIncomeLoss_54da92d9-5227-465b-a60e-9ba5e675f6bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_93150cd6-4f7c-4f23-9eb7-df28013fae1d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_93150cd6-4f7c-4f23-9eb7-df28013fae1d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_d6001685-73f3-49e8-b72a-300c4317ac58" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_93150cd6-4f7c-4f23-9eb7-df28013fae1d" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_d6001685-73f3-49e8-b72a-300c4317ac58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_d045e3a6-8887-40b2-a91c-9ba892cdc38d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_aa7feea8-9bd6-4eaa-9655-5925f8414de3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_93150cd6-4f7c-4f23-9eb7-df28013fae1d" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_aa7feea8-9bd6-4eaa-9655-5925f8414de3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_a8d6ae23-6b81-41b7-8be3-753bf741fde2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_a8d6ae23-6b81-41b7-8be3-753bf741fde2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_120baacd-6cd1-46bd-b9c2-6cd899bbf37f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_120baacd-6cd1-46bd-b9c2-6cd899bbf37f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_089b60cc-dcb2-4849-89f3-a7abda5374e7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_ProfitLoss_089b60cc-dcb2-4849-89f3-a7abda5374e7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_35bea1ae-6035-426a-af93-8665c3e051dc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_35bea1ae-6035-426a-af93-8665c3e051dc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_b2825412-1b20-4b9e-be6c-00237682c17a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_NetIncomeLoss_b2825412-1b20-4b9e-be6c-00237682c17a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_287b0d3c-9614-48d7-bde6-ccb0aa2f7977" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_us-gaap_EarningsPerShareAbstract_287b0d3c-9614-48d7-bde6-ccb0aa2f7977" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_7da9ef16-eb08-45a5-bf38-b54d7c1d2761" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_287b0d3c-9614-48d7-bde6-ccb0aa2f7977" xlink:to="loc_us-gaap_EarningsPerShareBasic_7da9ef16-eb08-45a5-bf38-b54d7c1d2761" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_22de14d0-96ab-4b4f-beb6-888187f44c29" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_287b0d3c-9614-48d7-bde6-ccb0aa2f7977" xlink:to="loc_us-gaap_EarningsPerShareDiluted_22de14d0-96ab-4b4f-beb6-888187f44c29" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_EarningsPerShareOtherDisclosureAbstract_39fc013c-8239-4e03-868d-105ab3e0d460" xlink:href="pwp-20240630.xsd#pwp_EarningsPerShareOtherDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5f8f45b4-e366-4899-8e53-c46693e21d55" xlink:to="loc_pwp_EarningsPerShareOtherDisclosureAbstract_39fc013c-8239-4e03-868d-105ab3e0d460" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_11ddf9f0-2993-4940-a049-a4a068eabfe3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pwp_EarningsPerShareOtherDisclosureAbstract_39fc013c-8239-4e03-868d-105ab3e0d460" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_11ddf9f0-2993-4940-a049-a4a068eabfe3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_c3d82724-47de-48b2-a568-aefd9243d288" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pwp_EarningsPerShareOtherDisclosureAbstract_39fc013c-8239-4e03-868d-105ab3e0d460" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_c3d82724-47de-48b2-a568-aefd9243d288" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/CondensedConsolidatedStatementsofChangesinEquityandRedeemableNonControllingInterestsUnaudited" xlink:type="simple" xlink:href="pwp-20240630.xsd#CondensedConsolidatedStatementsofChangesinEquityandRedeemableNonControllingInterestsUnaudited"/>
  <link:definitionLink xlink:role="http://pwp.com/role/CondensedConsolidatedStatementsofChangesinEquityandRedeemableNonControllingInterestsUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_3f5de88f-da41-4afd-bef2-eaa8987f8011" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_d31c6c1b-b288-44a1-9b8b-66717e443a68" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_3f5de88f-da41-4afd-bef2-eaa8987f8011" xlink:to="loc_us-gaap_StatementTable_d31c6c1b-b288-44a1-9b8b-66717e443a68" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_bb4ac7cf-a3cd-49fe-a335-003353243c79" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_d31c6c1b-b288-44a1-9b8b-66717e443a68" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_bb4ac7cf-a3cd-49fe-a335-003353243c79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_bb4ac7cf-a3cd-49fe-a335-003353243c79_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_bb4ac7cf-a3cd-49fe-a335-003353243c79" xlink:to="loc_us-gaap_EquityComponentDomain_bb4ac7cf-a3cd-49fe-a335-003353243c79_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_cb45fa98-b37c-4d28-9148-d49535489d8c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_bb4ac7cf-a3cd-49fe-a335-003353243c79" xlink:to="loc_us-gaap_EquityComponentDomain_cb45fa98-b37c-4d28-9148-d49535489d8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_2f5b0bb0-17c8-44e1-b6f2-84ac1ea8c4be" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cb45fa98-b37c-4d28-9148-d49535489d8c" xlink:to="loc_us-gaap_CommonStockMember_2f5b0bb0-17c8-44e1-b6f2-84ac1ea8c4be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_f9767214-23c2-40c5-8445-9e9fa2132e88" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cb45fa98-b37c-4d28-9148-d49535489d8c" xlink:to="loc_us-gaap_TreasuryStockCommonMember_f9767214-23c2-40c5-8445-9e9fa2132e88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_9b626286-ec60-423c-939c-6cf76d5f6254" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cb45fa98-b37c-4d28-9148-d49535489d8c" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_9b626286-ec60-423c-939c-6cf76d5f6254" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_1bc69642-7f26-4b57-a522-99ab22c36c63" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cb45fa98-b37c-4d28-9148-d49535489d8c" xlink:to="loc_us-gaap_RetainedEarningsMember_1bc69642-7f26-4b57-a522-99ab22c36c63" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_4259c956-4b38-4ad5-844e-0e0f46fb685b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cb45fa98-b37c-4d28-9148-d49535489d8c" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_4259c956-4b38-4ad5-844e-0e0f46fb685b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_8b357592-ef78-4e65-91df-0f7aeb624aac" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cb45fa98-b37c-4d28-9148-d49535489d8c" xlink:to="loc_us-gaap_NoncontrollingInterestMember_8b357592-ef78-4e65-91df-0f7aeb624aac" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_4351a3e8-4baf-4faf-a485-8a596b58b56b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_d31c6c1b-b288-44a1-9b8b-66717e443a68" xlink:to="loc_us-gaap_StatementClassOfStockAxis_4351a3e8-4baf-4faf-a485-8a596b58b56b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_4351a3e8-4baf-4faf-a485-8a596b58b56b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4351a3e8-4baf-4faf-a485-8a596b58b56b" xlink:to="loc_us-gaap_ClassOfStockDomain_4351a3e8-4baf-4faf-a485-8a596b58b56b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_35644a3c-af68-4d89-9326-55237135c991" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4351a3e8-4baf-4faf-a485-8a596b58b56b" xlink:to="loc_us-gaap_ClassOfStockDomain_35644a3c-af68-4d89-9326-55237135c991" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_d8be6a46-7657-47f2-9105-74cf2dfccd15" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_35644a3c-af68-4d89-9326-55237135c991" xlink:to="loc_us-gaap_CommonClassAMember_d8be6a46-7657-47f2-9105-74cf2dfccd15" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_f983eeeb-cb9e-4627-940e-feb47bb5a5fa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_35644a3c-af68-4d89-9326-55237135c991" xlink:to="loc_us-gaap_CommonClassBMember_f983eeeb-cb9e-4627-940e-feb47bb5a5fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3f5de88f-da41-4afd-bef2-eaa8987f8011" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_ef7a7e06-56f6-4513-95a6-4c2ad2526f17" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_ef7a7e06-56f6-4513-95a6-4c2ad2526f17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_d58b0b2b-a0ff-4fe0-9555-62ef347e834d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_TreasuryStockCommonShares_d58b0b2b-a0ff-4fe0-9555-62ef347e834d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_ec45a94c-b504-483d-920c-7d95162978d3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_ec45a94c-b504-483d-920c-7d95162978d3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_d1e8551d-d7af-4ce1-8f15-4bae984390da" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_ProfitLoss_d1e8551d-d7af-4ce1-8f15-4bae984390da" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_2c012b94-57c0-4258-8f4d-d726c60de086" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_NetIncomeLoss_2c012b94-57c0-4258-8f4d-d726c60de086" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_e6a14b3e-f7d8-4771-a5c0-5f26be7bbdb0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_e6a14b3e-f7d8-4771-a5c0-5f26be7bbdb0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountDistributions_b2c712a6-4a5a-4fa8-a7a0-0377f9d5b2cb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PartnersCapitalAccountDistributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_PartnersCapitalAccountDistributions_b2c712a6-4a5a-4fa8-a7a0-0377f9d5b2cb" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings_3bcb47fc-063a-4600-99c8-c5d2858bd11b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings_3bcb47fc-063a-4600-99c8-c5d2858bd11b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings_0a009ffc-1cc6-4227-8ab7-b01f74575cec" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings_0a009ffc-1cc6-4227-8ab7-b01f74575cec" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_98e6ff51-700d-4260-aef3-cecf781e8faf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_98e6ff51-700d-4260-aef3-cecf781e8faf" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Dividends_fd9ee16b-a5a5-47ee-945a-1dad52e2983a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Dividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_Dividends_fd9ee16b-a5a5-47ee-945a-1dad52e2983a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent_f435a618-2dee-4d68-a087-1cd2d349aa87" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent_f435a618-2dee-4d68-a087-1cd2d349aa87" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_1a0a44a8-e98e-4623-b3bd-8030f03ec1dd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_1a0a44a8-e98e-4623-b3bd-8030f03ec1dd" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityOther_7c25a968-e145-4b18-bc99-130c038ccb79" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_StockholdersEquityOther_7c25a968-e145-4b18-bc99-130c038ccb79" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_fd2731a4-27ee-413f-a33c-e3e6fdaf8687" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_fd2731a4-27ee-413f-a33c-e3e6fdaf8687" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_f0721af4-ec4a-47ad-aacc-e92fce0dd9f7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_f0721af4-ec4a-47ad-aacc-e92fce0dd9f7" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_b0918fde-d6b5-442e-bf91-fa40e5574bbe" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_b0918fde-d6b5-442e-bf91-fa40e5574bbe" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_377712fb-d2f2-4e1d-8b17-702bf324c61a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_377712fb-d2f2-4e1d-8b17-702bf324c61a" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_AdjustmentsToAdditionalPaidInCapitalChangeInOwnershipInterestValue_3fd292f1-0499-4417-8bd1-0f63e65d7a6b" xlink:href="pwp-20240630.xsd#pwp_AdjustmentsToAdditionalPaidInCapitalChangeInOwnershipInterestValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_pwp_AdjustmentsToAdditionalPaidInCapitalChangeInOwnershipInterestValue_3fd292f1-0499-4417-8bd1-0f63e65d7a6b" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_PaymentForTheExchangeOfPartnershipUnitsShares_c7bd410e-1c7f-4224-ba52-6c7c28961c8e" xlink:href="pwp-20240630.xsd#pwp_PaymentForTheExchangeOfPartnershipUnitsShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_pwp_PaymentForTheExchangeOfPartnershipUnitsShares_c7bd410e-1c7f-4224-ba52-6c7c28961c8e" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_AdditionalPaidInCapitalExchangeOfPartnershipUnits_68f899ad-f979-45f4-af23-4c9ef7d1912f" xlink:href="pwp-20240630.xsd#pwp_AdditionalPaidInCapitalExchangeOfPartnershipUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_pwp_AdditionalPaidInCapitalExchangeOfPartnershipUnits_68f899ad-f979-45f4-af23-4c9ef7d1912f" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_EffectOfMergerAndRelatedTransactionsShares_a4c6ba2e-7f0a-4fd0-b85f-ff072f52a3a5" xlink:href="pwp-20240630.xsd#pwp_EffectOfMergerAndRelatedTransactionsShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_pwp_EffectOfMergerAndRelatedTransactionsShares_a4c6ba2e-7f0a-4fd0-b85f-ff072f52a3a5" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_EffectOfMergerAndRelatedTransactionsValue_07d83bc4-19a3-429c-899a-ec756e613d81" xlink:href="pwp-20240630.xsd#pwp_EffectOfMergerAndRelatedTransactionsValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_pwp_EffectOfMergerAndRelatedTransactionsValue_07d83bc4-19a3-429c-899a-ec756e613d81" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_fae40627-60d3-45ac-a5c3-fa9d38821c8c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_fae40627-60d3-45ac-a5c3-fa9d38821c8c" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_56f0ffcf-78d9-43d1-8a3c-476b323d01b9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_56f0ffcf-78d9-43d1-8a3c-476b323d01b9" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestChangeInRedemptionValue_bf9517f4-d849-45bc-b7db-675819518032" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MinorityInterestChangeInRedemptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_cd1bdbf8-2de5-4a21-8dfd-31062eef3ef9" xlink:to="loc_us-gaap_MinorityInterestChangeInRedemptionValue_bf9517f4-d849-45bc-b7db-675819518032" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_55641f90-332f-4cbd-a425-fa1f7e8df8bf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_3bfe2d64-de5a-4fa5-81df-b27e0284efef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_09c8ceb0-1c6c-4893-a27f-cf55281f50b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInTemporaryEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3f5de88f-da41-4afd-bef2-eaa8987f8011" xlink:to="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests_e33193ae-7986-448d-bb44-964b679fac22" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests_e33193ae-7986-448d-bb44-964b679fac22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TemporaryEquityEffectOfMergerAndRelatedTransactionsValue_f4fa620d-339a-4be5-8423-e0d013750215" xlink:href="pwp-20240630.xsd#pwp_TemporaryEquityEffectOfMergerAndRelatedTransactionsValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_pwp_TemporaryEquityEffectOfMergerAndRelatedTransactionsValue_f4fa620d-339a-4be5-8423-e0d013750215" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityNetIncome_3ebd2879-1b27-409b-a2e7-15b7e17642b9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityNetIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_us-gaap_TemporaryEquityNetIncome_3ebd2879-1b27-409b-a2e7-15b7e17642b9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TemporaryEquityEquityBasedAwards_4d33b513-a2ae-4a2a-ba1a-7297718c0399" xlink:href="pwp-20240630.xsd#pwp_TemporaryEquityEquityBasedAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_pwp_TemporaryEquityEquityBasedAwards_4d33b513-a2ae-4a2a-ba1a-7297718c0399" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TemporaryEquityPartnersCapitalAccountDistributions_6c854ace-218f-4d82-8d5c-c889cec849ae" xlink:href="pwp-20240630.xsd#pwp_TemporaryEquityPartnersCapitalAccountDistributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_pwp_TemporaryEquityPartnersCapitalAccountDistributions_6c854ace-218f-4d82-8d5c-c889cec849ae" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TemporaryEquityShareBasedPaymentArrangementDecreaseForTaxWithholdingObligation_f641a3f7-81be-44c1-aa58-1b05aeea58ef" xlink:href="pwp-20240630.xsd#pwp_TemporaryEquityShareBasedPaymentArrangementDecreaseForTaxWithholdingObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_pwp_TemporaryEquityShareBasedPaymentArrangementDecreaseForTaxWithholdingObligation_f641a3f7-81be-44c1-aa58-1b05aeea58ef" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityForeignCurrencyTranslationAdjustments_0a9152ea-9b6a-4077-b918-e6666346c223" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityForeignCurrencyTranslationAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_us-gaap_TemporaryEquityForeignCurrencyTranslationAdjustments_0a9152ea-9b6a-4077-b918-e6666346c223" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityOtherChanges_fdd5225b-9f19-4772-b696-c78f40c058c3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityOtherChanges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_us-gaap_TemporaryEquityOtherChanges_fdd5225b-9f19-4772-b696-c78f40c058c3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TemporaryEquityConversionOfConvertibleSecurities_6d05dea9-91ee-4327-9d76-398017fb3cc3" xlink:href="pwp-20240630.xsd#pwp_TemporaryEquityConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_pwp_TemporaryEquityConversionOfConvertibleSecurities_6d05dea9-91ee-4327-9d76-398017fb3cc3" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TemporaryEquityAdjustmentsToAdditionalPaidInCapitalChangeInOwnershipInterestValue_b4fbd469-845f-4285-901f-cf0c150f1784" xlink:href="pwp-20240630.xsd#pwp_TemporaryEquityAdjustmentsToAdditionalPaidInCapitalChangeInOwnershipInterestValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_pwp_TemporaryEquityAdjustmentsToAdditionalPaidInCapitalChangeInOwnershipInterestValue_b4fbd469-845f-4285-901f-cf0c150f1784" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_RedeemableNoncontrollingInterestChangeInRedemptionValue_b7ae822c-4e87-4674-83a6-12fc56fe8440" xlink:href="pwp-20240630.xsd#pwp_RedeemableNoncontrollingInterestChangeInRedemptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_9d7b6498-c976-4440-bc1b-d8a4c0674f80" xlink:to="loc_pwp_RedeemableNoncontrollingInterestChangeInRedemptionValue_b7ae822c-4e87-4674-83a6-12fc56fe8440" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests_fad8b53b-c4f0-4cb6-9aaf-f78c77601f71" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/CondensedConsolidatedStatementsofChangesinEquityandRedeemableNonControllingInterestsUnauditedParenthetical" xlink:type="simple" xlink:href="pwp-20240630.xsd#CondensedConsolidatedStatementsofChangesinEquityandRedeemableNonControllingInterestsUnauditedParenthetical"/>
  <link:definitionLink xlink:role="http://pwp.com/role/CondensedConsolidatedStatementsofChangesinEquityandRedeemableNonControllingInterestsUnauditedParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_b86b82fe-890e-47f6-b0b0-9d26a8a48925" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_631b7885-c0e6-4dcb-a328-0a098bc9517e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_b86b82fe-890e-47f6-b0b0-9d26a8a48925" xlink:to="loc_us-gaap_StatementTable_631b7885-c0e6-4dcb-a328-0a098bc9517e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_106c8d1a-0fa4-420f-b052-64b9d267d289" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_631b7885-c0e6-4dcb-a328-0a098bc9517e" xlink:to="loc_us-gaap_StatementClassOfStockAxis_106c8d1a-0fa4-420f-b052-64b9d267d289" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_106c8d1a-0fa4-420f-b052-64b9d267d289_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_106c8d1a-0fa4-420f-b052-64b9d267d289" xlink:to="loc_us-gaap_ClassOfStockDomain_106c8d1a-0fa4-420f-b052-64b9d267d289_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_c121adcd-8df1-44ef-a502-35441bc0b33a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_106c8d1a-0fa4-420f-b052-64b9d267d289" xlink:to="loc_us-gaap_ClassOfStockDomain_c121adcd-8df1-44ef-a502-35441bc0b33a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_b83bc1ac-ba45-4854-bc3c-4be1aee7016c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_c121adcd-8df1-44ef-a502-35441bc0b33a" xlink:to="loc_us-gaap_CommonClassAMember_b83bc1ac-ba45-4854-bc3c-4be1aee7016c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_d1f070e9-7b4d-4168-b2de-b312e532c7d2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b86b82fe-890e-47f6-b0b0-9d26a8a48925" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_d1f070e9-7b4d-4168-b2de-b312e532c7d2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/SummaryofSignificantAccountingPoliciesDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#SummaryofSignificantAccountingPoliciesDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/SummaryofSignificantAccountingPoliciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_dda77b46-3016-4154-bc7d-defeafb59df7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_c61496e1-992c-489b-8b41-ac1d54f357e4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_dda77b46-3016-4154-bc7d-defeafb59df7" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_c61496e1-992c-489b-8b41-ac1d54f357e4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_f84c3e17-8ffb-40c7-8dc9-77ff4e7a9f85" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_c61496e1-992c-489b-8b41-ac1d54f357e4" xlink:to="loc_srt_ConsolidatedEntitiesAxis_f84c3e17-8ffb-40c7-8dc9-77ff4e7a9f85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_f84c3e17-8ffb-40c7-8dc9-77ff4e7a9f85_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_f84c3e17-8ffb-40c7-8dc9-77ff4e7a9f85" xlink:to="loc_srt_ConsolidatedEntitiesDomain_f84c3e17-8ffb-40c7-8dc9-77ff4e7a9f85_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_0ad5e511-81ee-4cfb-ba0b-4065cdaa6633" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_f84c3e17-8ffb-40c7-8dc9-77ff4e7a9f85" xlink:to="loc_srt_ConsolidatedEntitiesDomain_0ad5e511-81ee-4cfb-ba0b-4065cdaa6633" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_PWPOpCoMember_72bcace4-4ef9-4004-9858-a61a63238c41" xlink:href="pwp-20240630.xsd#pwp_PWPOpCoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_0ad5e511-81ee-4cfb-ba0b-4065cdaa6633" xlink:to="loc_pwp_PWPOpCoMember_72bcace4-4ef9-4004-9858-a61a63238c41" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsNet_abffc862-9687-4523-a1eb-c4ade15f7cc8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_dda77b46-3016-4154-bc7d-defeafb59df7" xlink:to="loc_us-gaap_AssetsNet_abffc862-9687-4523-a1eb-c4ade15f7cc8" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/RevenueandReceivablesfromContractswithCustomersScheduleofDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#RevenueandReceivablesfromContractswithCustomersScheduleofDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/RevenueandReceivablesfromContractswithCustomersScheduleofDisaggregationofRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_a436d63b-8cad-4a1b-be62-e9c2e5f3ddb4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_204a101a-2066-4c6b-919f-18734ee796c6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_a436d63b-8cad-4a1b-be62-e9c2e5f3ddb4" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_204a101a-2066-4c6b-919f-18734ee796c6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_ae612288-3e8c-4514-b35c-1d8153e8c7b9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TimingOfTransferOfGoodOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_204a101a-2066-4c6b-919f-18734ee796c6" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_ae612288-3e8c-4514-b35c-1d8153e8c7b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_ae612288-3e8c-4514-b35c-1d8153e8c7b9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_ae612288-3e8c-4514-b35c-1d8153e8c7b9" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_ae612288-3e8c-4514-b35c-1d8153e8c7b9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_79d3f131-3a90-4997-9125-bd310e99a2b7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_ae612288-3e8c-4514-b35c-1d8153e8c7b9" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_79d3f131-3a90-4997-9125-bd310e99a2b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredOverTimeMember_a6b00ae7-9b34-47b1-8b57-69c1c79ba45c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransferredOverTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_79d3f131-3a90-4997-9125-bd310e99a2b7" xlink:to="loc_us-gaap_TransferredOverTimeMember_a6b00ae7-9b34-47b1-8b57-69c1c79ba45c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredAtPointInTimeMember_a8dd1aaf-aa33-403f-b36d-24e85c14df84" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransferredAtPointInTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_79d3f131-3a90-4997-9125-bd310e99a2b7" xlink:to="loc_us-gaap_TransferredAtPointInTimeMember_a8dd1aaf-aa33-403f-b36d-24e85c14df84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c12f89f7-7076-413c-9754-53ae0bb63535" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_a436d63b-8cad-4a1b-be62-e9c2e5f3ddb4" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c12f89f7-7076-413c-9754-53ae0bb63535" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/RevenueandReceivablesfromContractswithCustomersAdditionalInformationDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#RevenueandReceivablesfromContractswithCustomersAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/RevenueandReceivablesfromContractswithCustomersAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_54120018-b410-4109-ab0f-36b7270bfbe9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_54120018-b410-4109-ab0f-36b7270bfbe9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_4406d0d4-ace9-4202-a01d-642685545f35" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:to="loc_srt_MajorCustomersAxis_4406d0d4-ace9-4202-a01d-642685545f35" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_4406d0d4-ace9-4202-a01d-642685545f35_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_4406d0d4-ace9-4202-a01d-642685545f35" xlink:to="loc_srt_NameOfMajorCustomerDomain_4406d0d4-ace9-4202-a01d-642685545f35_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_97b7b08d-0df6-4362-94a9-36b2aa654e9e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_4406d0d4-ace9-4202-a01d-642685545f35" xlink:to="loc_srt_NameOfMajorCustomerDomain_97b7b08d-0df6-4362-94a9-36b2aa654e9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_OneCustomerMember_7b74ecb7-70a5-4e8e-ba86-a0c3f0f0a42b" xlink:href="pwp-20240630.xsd#pwp_OneCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_97b7b08d-0df6-4362-94a9-36b2aa654e9e" xlink:to="loc_pwp_OneCustomerMember_7b74ecb7-70a5-4e8e-ba86-a0c3f0f0a42b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TwoCustomersMember_552af5d6-9243-47c8-889d-02624c248faa" xlink:href="pwp-20240630.xsd#pwp_TwoCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_97b7b08d-0df6-4362-94a9-36b2aa654e9e" xlink:to="loc_pwp_TwoCustomersMember_552af5d6-9243-47c8-889d-02624c248faa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_754470f7-17dd-48e0-9ff4-1745d66f576f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_754470f7-17dd-48e0-9ff4-1745d66f576f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_754470f7-17dd-48e0-9ff4-1745d66f576f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_754470f7-17dd-48e0-9ff4-1745d66f576f" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_754470f7-17dd-48e0-9ff4-1745d66f576f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_be32bd58-51a4-433b-b21b-fbcaac11fb07" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_754470f7-17dd-48e0-9ff4-1745d66f576f" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_be32bd58-51a4-433b-b21b-fbcaac11fb07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableMember_acef1842-5131-4d05-aaa8-cc43caae462d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_be32bd58-51a4-433b-b21b-fbcaac11fb07" xlink:to="loc_us-gaap_AccountsReceivableMember_acef1842-5131-4d05-aaa8-cc43caae462d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_f7054496-a568-4179-acd1-67fb7b8cf39e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_f7054496-a568-4179-acd1-67fb7b8cf39e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_f7054496-a568-4179-acd1-67fb7b8cf39e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_f7054496-a568-4179-acd1-67fb7b8cf39e" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_f7054496-a568-4179-acd1-67fb7b8cf39e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_30c89312-9efc-4e86-9b9c-98335ea4fc5a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_f7054496-a568-4179-acd1-67fb7b8cf39e" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_30c89312-9efc-4e86-9b9c-98335ea4fc5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_d1147957-e829-4be0-850a-a46e2f880d1b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_30c89312-9efc-4e86-9b9c-98335ea4fc5a" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_d1147957-e829-4be0-850a-a46e2f880d1b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ReimbursableExpensesRecordedAsRevenue_b4de4637-d234-4c81-82ca-076adcae71c1" xlink:href="pwp-20240630.xsd#pwp_ReimbursableExpensesRecordedAsRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_pwp_ReimbursableExpensesRecordedAsRevenue_b4de4637-d234-4c81-82ca-076adcae71c1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_ecb5cbf7-0cb2-4b59-9b3d-13536278da80" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_ecb5cbf7-0cb2-4b59-9b3d-13536278da80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_8e9ef4d2-8b2d-45fe-9e67-f7034441cba8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_8e9ef4d2-8b2d-45fe-9e67-f7034441cba8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_5c4fab94-5121-4a76-b100-6fb6964893cf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_5c4fab94-5121-4a76-b100-6fb6964893cf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_0e1cb359-66e6-4e23-bbd6-47ef340531ab" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_ContractWithCustomerLiability_0e1cb359-66e6-4e23-bbd6-47ef340531ab" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_c9154c1d-efbb-48ce-b929-d8f91833d11b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_c9154c1d-efbb-48ce-b929-d8f91833d11b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedFeesAndOtherRevenueReceivable_63a44c28-32b8-489e-ab02-cdc53289879e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccruedFeesAndOtherRevenueReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_AccruedFeesAndOtherRevenueReceivable_63a44c28-32b8-489e-ab02-cdc53289879e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_97ec3e1e-3b49-44c7-9744-0f67aa765642" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_AccountsReceivableNet_97ec3e1e-3b49-44c7-9744-0f67aa765642" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/RevenueandReceivablesfromContractswithCustomersAdditionalInformationDetails_1" xlink:type="simple" xlink:href="pwp-20240630.xsd#RevenueandReceivablesfromContractswithCustomersAdditionalInformationDetails_1"/>
  <link:definitionLink xlink:role="http://pwp.com/role/RevenueandReceivablesfromContractswithCustomersAdditionalInformationDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_4406d0d4-ace9-4202-a01d-642685545f35" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:to="loc_srt_MajorCustomersAxis_4406d0d4-ace9-4202-a01d-642685545f35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_4406d0d4-ace9-4202-a01d-642685545f35_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_4406d0d4-ace9-4202-a01d-642685545f35" xlink:to="loc_srt_NameOfMajorCustomerDomain_4406d0d4-ace9-4202-a01d-642685545f35_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_97b7b08d-0df6-4362-94a9-36b2aa654e9e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_4406d0d4-ace9-4202-a01d-642685545f35" xlink:to="loc_srt_NameOfMajorCustomerDomain_97b7b08d-0df6-4362-94a9-36b2aa654e9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_OneCustomerMember_7b74ecb7-70a5-4e8e-ba86-a0c3f0f0a42b" xlink:href="pwp-20240630.xsd#pwp_OneCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_97b7b08d-0df6-4362-94a9-36b2aa654e9e" xlink:to="loc_pwp_OneCustomerMember_7b74ecb7-70a5-4e8e-ba86-a0c3f0f0a42b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TwoCustomersMember_552af5d6-9243-47c8-889d-02624c248faa" xlink:href="pwp-20240630.xsd#pwp_TwoCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_97b7b08d-0df6-4362-94a9-36b2aa654e9e" xlink:to="loc_pwp_TwoCustomersMember_552af5d6-9243-47c8-889d-02624c248faa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_754470f7-17dd-48e0-9ff4-1745d66f576f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_754470f7-17dd-48e0-9ff4-1745d66f576f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_754470f7-17dd-48e0-9ff4-1745d66f576f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_754470f7-17dd-48e0-9ff4-1745d66f576f" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_754470f7-17dd-48e0-9ff4-1745d66f576f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_be32bd58-51a4-433b-b21b-fbcaac11fb07" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_754470f7-17dd-48e0-9ff4-1745d66f576f" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_be32bd58-51a4-433b-b21b-fbcaac11fb07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableMember_acef1842-5131-4d05-aaa8-cc43caae462d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_be32bd58-51a4-433b-b21b-fbcaac11fb07" xlink:to="loc_us-gaap_AccountsReceivableMember_acef1842-5131-4d05-aaa8-cc43caae462d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_f7054496-a568-4179-acd1-67fb7b8cf39e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_64ca7417-0628-4ec6-97db-47b568d19049" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_f7054496-a568-4179-acd1-67fb7b8cf39e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_f7054496-a568-4179-acd1-67fb7b8cf39e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_f7054496-a568-4179-acd1-67fb7b8cf39e" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_f7054496-a568-4179-acd1-67fb7b8cf39e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_30c89312-9efc-4e86-9b9c-98335ea4fc5a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_f7054496-a568-4179-acd1-67fb7b8cf39e" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_30c89312-9efc-4e86-9b9c-98335ea4fc5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_d1147957-e829-4be0-850a-a46e2f880d1b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_30c89312-9efc-4e86-9b9c-98335ea4fc5a" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_d1147957-e829-4be0-850a-a46e2f880d1b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ReimbursableExpensesRecordedAsRevenue_b4de4637-d234-4c81-82ca-076adcae71c1" xlink:href="pwp-20240630.xsd#pwp_ReimbursableExpensesRecordedAsRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_pwp_ReimbursableExpensesRecordedAsRevenue_b4de4637-d234-4c81-82ca-076adcae71c1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_ecb5cbf7-0cb2-4b59-9b3d-13536278da80" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_ecb5cbf7-0cb2-4b59-9b3d-13536278da80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_8e9ef4d2-8b2d-45fe-9e67-f7034441cba8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_8e9ef4d2-8b2d-45fe-9e67-f7034441cba8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_5c4fab94-5121-4a76-b100-6fb6964893cf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_5c4fab94-5121-4a76-b100-6fb6964893cf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_0e1cb359-66e6-4e23-bbd6-47ef340531ab" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_ContractWithCustomerLiability_0e1cb359-66e6-4e23-bbd6-47ef340531ab" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_c9154c1d-efbb-48ce-b929-d8f91833d11b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_c9154c1d-efbb-48ce-b929-d8f91833d11b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedFeesAndOtherRevenueReceivable_63a44c28-32b8-489e-ab02-cdc53289879e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccruedFeesAndOtherRevenueReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_AccruedFeesAndOtherRevenueReceivable_63a44c28-32b8-489e-ab02-cdc53289879e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_97ec3e1e-3b49-44c7-9744-0f67aa765642" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_0f245b6d-5f73-4f63-bd06-bacf2fa3353b" xlink:to="loc_us-gaap_AccountsReceivableNet_97ec3e1e-3b49-44c7-9744-0f67aa765642" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/IntangibleAssetsSummaryofComponentsofGrossandNetIntangibleAssetDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#IntangibleAssetsSummaryofComponentsofGrossandNetIntangibleAssetDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/IntangibleAssetsSummaryofComponentsofGrossandNetIntangibleAssetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_3ad7b822-7e82-48e6-90f7-c2e175baa320" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_61a61560-e738-4db0-8a35-9cb2caaa0f0a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_3ad7b822-7e82-48e6-90f7-c2e175baa320" xlink:to="loc_us-gaap_StatementTable_61a61560-e738-4db0-8a35-9cb2caaa0f0a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a693c540-1ff4-4ff8-aeff-db7198ccb766" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_61a61560-e738-4db0-8a35-9cb2caaa0f0a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a693c540-1ff4-4ff8-aeff-db7198ccb766" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a693c540-1ff4-4ff8-aeff-db7198ccb766_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a693c540-1ff4-4ff8-aeff-db7198ccb766" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a693c540-1ff4-4ff8-aeff-db7198ccb766_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d33c321c-0810-4749-bded-a3d244c9f7a9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a693c540-1ff4-4ff8-aeff-db7198ccb766" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d33c321c-0810-4749-bded-a3d244c9f7a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_2127bfe9-4c61-4799-b759-da4fad438b23" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d33c321c-0810-4749-bded-a3d244c9f7a9" xlink:to="loc_us-gaap_CustomerRelationshipsMember_2127bfe9-4c61-4799-b759-da4fad438b23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_6ce7042a-dfb1-4f0a-95df-3363b58f2c54" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d33c321c-0810-4749-bded-a3d244c9f7a9" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_6ce7042a-dfb1-4f0a-95df-3363b58f2c54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_3ac857f6-1818-4944-be30-8b519dba417f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3ad7b822-7e82-48e6-90f7-c2e175baa320" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_3ac857f6-1818-4944-be30-8b519dba417f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_84ef645d-cc52-44bc-a30a-27460c4af6fc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3ad7b822-7e82-48e6-90f7-c2e175baa320" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_84ef645d-cc52-44bc-a30a-27460c4af6fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_b17d4b72-e181-4ddd-870d-973934b3af6c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3ad7b822-7e82-48e6-90f7-c2e175baa320" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_b17d4b72-e181-4ddd-870d-973934b3af6c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/FixedAssetsSummaryofFixedAssetsDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#FixedAssetsSummaryofFixedAssetsDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/FixedAssetsSummaryofFixedAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_3ab69475-b23f-485d-a5f6-10e912280e95" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_4609c11a-85c0-4b0d-8bb7-f5bfcb6f8665" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_3ab69475-b23f-485d-a5f6-10e912280e95" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_4609c11a-85c0-4b0d-8bb7-f5bfcb6f8665" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_7a090090-0f5c-4ad7-9a96-76d174f843a5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_4609c11a-85c0-4b0d-8bb7-f5bfcb6f8665" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_7a090090-0f5c-4ad7-9a96-76d174f843a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_7a090090-0f5c-4ad7-9a96-76d174f843a5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_7a090090-0f5c-4ad7-9a96-76d174f843a5" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_7a090090-0f5c-4ad7-9a96-76d174f843a5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_c9d8d1e0-e785-440f-b375-3ac782365f7e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_7a090090-0f5c-4ad7-9a96-76d174f843a5" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_c9d8d1e0-e785-440f-b375-3ac782365f7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_87fffb39-6760-42af-8356-d5bbff257e50" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_c9d8d1e0-e785-440f-b375-3ac782365f7e" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_87fffb39-6760-42af-8356-d5bbff257e50" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_52880165-ceeb-41fe-8079-e2364d2cba88" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_c9d8d1e0-e785-440f-b375-3ac782365f7e" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_52880165-ceeb-41fe-8079-e2364d2cba88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquipmentMember_5be1c1c0-0fe9-4f57-a9ca-97f6ae86ada4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_c9d8d1e0-e785-440f-b375-3ac782365f7e" xlink:to="loc_us-gaap_EquipmentMember_5be1c1c0-0fe9-4f57-a9ca-97f6ae86ada4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_SoftwareMember_4283ca33-cbf1-490a-bf20-5b8b01b6c81d" xlink:href="pwp-20240630.xsd#pwp_SoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_c9d8d1e0-e785-440f-b375-3ac782365f7e" xlink:to="loc_pwp_SoftwareMember_4283ca33-cbf1-490a-bf20-5b8b01b6c81d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_f9441e25-0dea-4580-8be9-78ada419674e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_3ab69475-b23f-485d-a5f6-10e912280e95" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_f9441e25-0dea-4580-8be9-78ada419674e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_beae1d78-0d4b-4349-ac0c-f3b31ddc155c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_3ab69475-b23f-485d-a5f6-10e912280e95" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_beae1d78-0d4b-4349-ac0c-f3b31ddc155c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_0c375638-2b4c-40e1-b616-c426295204e7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_3ab69475-b23f-485d-a5f6-10e912280e95" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_0c375638-2b4c-40e1-b616-c426295204e7" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/StockholdersEquityandRedeemableNonControllingInterestsDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#StockholdersEquityandRedeemableNonControllingInterestsDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/StockholdersEquityandRedeemableNonControllingInterestsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_1365927b-8074-4db0-a8ab-b72dba0aca26" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_1365927b-8074-4db0-a8ab-b72dba0aca26" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_4da3fc74-61d6-45f2-9c8f-943c8e26686b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1365927b-8074-4db0-a8ab-b72dba0aca26" xlink:to="loc_us-gaap_StatementClassOfStockAxis_4da3fc74-61d6-45f2-9c8f-943c8e26686b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_4da3fc74-61d6-45f2-9c8f-943c8e26686b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4da3fc74-61d6-45f2-9c8f-943c8e26686b" xlink:to="loc_us-gaap_ClassOfStockDomain_4da3fc74-61d6-45f2-9c8f-943c8e26686b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_7337fcff-11b3-424e-9f72-79eb990f5113" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4da3fc74-61d6-45f2-9c8f-943c8e26686b" xlink:to="loc_us-gaap_ClassOfStockDomain_7337fcff-11b3-424e-9f72-79eb990f5113" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_51cbaef8-d423-4d1a-8bd8-d0b2b19d1fb5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_7337fcff-11b3-424e-9f72-79eb990f5113" xlink:to="loc_us-gaap_CommonClassAMember_51cbaef8-d423-4d1a-8bd8-d0b2b19d1fb5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_49aa8583-138f-4851-ab2a-9b63501a9592" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1365927b-8074-4db0-a8ab-b72dba0aca26" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_49aa8583-138f-4851-ab2a-9b63501a9592" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_49aa8583-138f-4851-ab2a-9b63501a9592_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_49aa8583-138f-4851-ab2a-9b63501a9592" xlink:to="loc_us-gaap_EquityComponentDomain_49aa8583-138f-4851-ab2a-9b63501a9592_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_84a83938-890e-4d83-bcf6-d47956e06d49" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_49aa8583-138f-4851-ab2a-9b63501a9592" xlink:to="loc_us-gaap_EquityComponentDomain_84a83938-890e-4d83-bcf6-d47956e06d49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_ae88e950-b807-4212-a36a-a2b69a1dd7d0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_84a83938-890e-4d83-bcf6-d47956e06d49" xlink:to="loc_us-gaap_CommonStockMember_ae88e950-b807-4212-a36a-a2b69a1dd7d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_7f5892f3-05db-4e1b-a7e4-41f2dd0647cc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1365927b-8074-4db0-a8ab-b72dba0aca26" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_7f5892f3-05db-4e1b-a7e4-41f2dd0647cc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_7f5892f3-05db-4e1b-a7e4-41f2dd0647cc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_7f5892f3-05db-4e1b-a7e4-41f2dd0647cc" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_7f5892f3-05db-4e1b-a7e4-41f2dd0647cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_720f3834-ee14-4f98-8c1f-99b98c0a18e2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_7f5892f3-05db-4e1b-a7e4-41f2dd0647cc" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_720f3834-ee14-4f98-8c1f-99b98c0a18e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrivatePlacementMember_a4ca6a52-b036-4fe7-9225-9d9e6aa436d4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PrivatePlacementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_720f3834-ee14-4f98-8c1f-99b98c0a18e2" xlink:to="loc_us-gaap_PrivatePlacementMember_a4ca6a52-b036-4fe7-9225-9d9e6aa436d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_f99b3696-d752-4933-8fc6-0e19f89481e4" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1365927b-8074-4db0-a8ab-b72dba0aca26" xlink:to="loc_srt_OwnershipAxis_f99b3696-d752-4933-8fc6-0e19f89481e4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_f99b3696-d752-4933-8fc6-0e19f89481e4_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_f99b3696-d752-4933-8fc6-0e19f89481e4" xlink:to="loc_srt_OwnershipDomain_f99b3696-d752-4933-8fc6-0e19f89481e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_8c4b8978-bcde-41ac-9411-27655c09b70c" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_f99b3696-d752-4933-8fc6-0e19f89481e4" xlink:to="loc_srt_OwnershipDomain_8c4b8978-bcde-41ac-9411-27655c09b70c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ProfessionalPartnersAndIlpsMember_7de2f688-c160-41c8-996f-b8388e1e8521" xlink:href="pwp-20240630.xsd#pwp_ProfessionalPartnersAndIlpsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_8c4b8978-bcde-41ac-9411-27655c09b70c" xlink:to="loc_pwp_ProfessionalPartnersAndIlpsMember_7de2f688-c160-41c8-996f-b8388e1e8521" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_037f087f-3ef7-4ce5-a468-76bcb1898961" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1365927b-8074-4db0-a8ab-b72dba0aca26" xlink:to="loc_srt_RangeAxis_037f087f-3ef7-4ce5-a468-76bcb1898961" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_037f087f-3ef7-4ce5-a468-76bcb1898961_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_037f087f-3ef7-4ce5-a468-76bcb1898961" xlink:to="loc_srt_RangeMember_037f087f-3ef7-4ce5-a468-76bcb1898961_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f32ad074-ba6f-40b0-bd28-303080bff5ab" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_037f087f-3ef7-4ce5-a468-76bcb1898961" xlink:to="loc_srt_RangeMember_f32ad074-ba6f-40b0-bd28-303080bff5ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_f034aa55-27bc-4094-945a-2994332f7782" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f32ad074-ba6f-40b0-bd28-303080bff5ab" xlink:to="loc_srt_MinimumMember_f034aa55-27bc-4094-945a-2994332f7782" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_ff0bd061-7a68-46c8-a52e-d1581b436c5b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f32ad074-ba6f-40b0-bd28-303080bff5ab" xlink:to="loc_srt_MaximumMember_ff0bd061-7a68-46c8-a52e-d1581b436c5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_fa50c305-a6dc-4e81-9c70-89368241b4e1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1365927b-8074-4db0-a8ab-b72dba0aca26" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_fa50c305-a6dc-4e81-9c70-89368241b4e1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_fa50c305-a6dc-4e81-9c70-89368241b4e1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_fa50c305-a6dc-4e81-9c70-89368241b4e1" xlink:to="loc_us-gaap_RelatedPartyDomain_fa50c305-a6dc-4e81-9c70-89368241b4e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_e30dbcdc-8acb-4778-bea9-823369de3b96" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_fa50c305-a6dc-4e81-9c70-89368241b4e1" xlink:to="loc_us-gaap_RelatedPartyDomain_e30dbcdc-8acb-4778-bea9-823369de3b96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_WorkingPartnersMember_745f6bfd-38f6-4326-8c7f-516f6d9a881f" xlink:href="pwp-20240630.xsd#pwp_WorkingPartnersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_e30dbcdc-8acb-4778-bea9-823369de3b96" xlink:to="loc_pwp_WorkingPartnersMember_745f6bfd-38f6-4326-8c7f-516f6d9a881f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_9012378c-e5b1-46d3-9012-e4b8f4f276b7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1365927b-8074-4db0-a8ab-b72dba0aca26" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_9012378c-e5b1-46d3-9012-e4b8f4f276b7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_9012378c-e5b1-46d3-9012-e4b8f4f276b7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_9012378c-e5b1-46d3-9012-e4b8f4f276b7" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_9012378c-e5b1-46d3-9012-e4b8f4f276b7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_cd1e764e-80bf-4444-a71a-8b051fe48048" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_9012378c-e5b1-46d3-9012-e4b8f4f276b7" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_cd1e764e-80bf-4444-a71a-8b051fe48048" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_FounderSharePurchaseOptionMember_750276c0-d2f5-4174-9a90-d8c1eedae8b8" xlink:href="pwp-20240630.xsd#pwp_FounderSharePurchaseOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_cd1e764e-80bf-4444-a71a-8b051fe48048" xlink:to="loc_pwp_FounderSharePurchaseOptionMember_750276c0-d2f5-4174-9a90-d8c1eedae8b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_a3770b12-a783-49df-8976-685114234e12" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_a3770b12-a783-49df-8976-685114234e12" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_6dc2bb5e-67b3-4281-9727-58761a092cf3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_6dc2bb5e-67b3-4281-9727-58761a092cf3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_e24f0ee5-bfc6-4cbb-bf68-248904d80f46" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_e24f0ee5-bfc6-4cbb-bf68-248904d80f46" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_331c5cde-ca7a-41bb-8724-3e100537cf0a" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_331c5cde-ca7a-41bb-8724-3e100537cf0a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_e8e41408-13c8-4dbc-a8fe-1f351a9e17e1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_e8e41408-13c8-4dbc-a8fe-1f351a9e17e1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfEquity_cada87d7-9288-4ba8-995b-f7a9f85148c0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsForRepurchaseOfEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfEquity_cada87d7-9288-4ba8-995b-f7a9f85148c0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_3a03b9a4-9f87-4212-8ccf-fa6c76808ba0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_3a03b9a4-9f87-4212-8ccf-fa6c76808ba0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_UnitsOfMinorityInterestAmount_f90deaff-40f7-4f87-95b4-29d0408b2d61" xlink:href="pwp-20240630.xsd#pwp_UnitsOfMinorityInterestAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_pwp_UnitsOfMinorityInterestAmount_f90deaff-40f7-4f87-95b4-29d0408b2d61" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_8a66190a-19df-4f2f-aea7-ac968c54f91f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_8a66190a-19df-4f2f-aea7-ac968c54f91f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_StockholdersEquityNoteConversionRatio_1b509801-22ec-4c16-9c95-2d55cb31aea6" xlink:href="pwp-20240630.xsd#pwp_StockholdersEquityNoteConversionRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_pwp_StockholdersEquityNoteConversionRatio_1b509801-22ec-4c16-9c95-2d55cb31aea6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_DistributionRate_409dfdcb-d773-4173-b8ed-3884097b0107" xlink:href="pwp-20240630.xsd#pwp_DistributionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_pwp_DistributionRate_409dfdcb-d773-4173-b8ed-3884097b0107" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_LockUpPeriod_d12c19d1-0dcf-4168-a540-6fffa79f8402" xlink:href="pwp-20240630.xsd#pwp_LockUpPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_pwp_LockUpPeriod_d12c19d1-0dcf-4168-a540-6fffa79f8402" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_PaymentForTheExchangeOfPartnershipUnits_c0ea3989-16b4-4288-94e4-3787dffb6a79" xlink:href="pwp-20240630.xsd#pwp_PaymentForTheExchangeOfPartnershipUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_pwp_PaymentForTheExchangeOfPartnershipUnits_c0ea3989-16b4-4288-94e4-3787dffb6a79" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_AccruedPaymentForTheExchangeOfPartnershipUnits_e3d19085-b493-4bd2-af7b-f64734647c8b" xlink:href="pwp-20240630.xsd#pwp_AccruedPaymentForTheExchangeOfPartnershipUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_pwp_AccruedPaymentForTheExchangeOfPartnershipUnits_e3d19085-b493-4bd2-af7b-f64734647c8b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_2622a03a-57bc-44ee-86ae-ee851ba78e0f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_2622a03a-57bc-44ee-86ae-ee851ba78e0f" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_3bc3434c-fb63-4212-97bd-8838853e5780" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1ba32d4c-1ce9-4413-9599-dd507ce0d2e2" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_3bc3434c-fb63-4212-97bd-8838853e5780" xlink:type="arc" order="15"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/DebtDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#DebtDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/DebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_c0b79784-42ff-4de6-aa7f-7a79343b29eb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_2f93f9e0-b933-409e-a317-8069d4b0ea0c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c0b79784-42ff-4de6-aa7f-7a79343b29eb" xlink:to="loc_us-gaap_DebtInstrumentTable_2f93f9e0-b933-409e-a317-8069d4b0ea0c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_be49c64b-ab45-4383-a4d1-388fb6a648d1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_2f93f9e0-b933-409e-a317-8069d4b0ea0c" xlink:to="loc_us-gaap_CreditFacilityAxis_be49c64b-ab45-4383-a4d1-388fb6a648d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_be49c64b-ab45-4383-a4d1-388fb6a648d1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_be49c64b-ab45-4383-a4d1-388fb6a648d1" xlink:to="loc_us-gaap_CreditFacilityDomain_be49c64b-ab45-4383-a4d1-388fb6a648d1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_87fcae26-493d-45a5-80d5-0f651c97632f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_be49c64b-ab45-4383-a4d1-388fb6a648d1" xlink:to="loc_us-gaap_CreditFacilityDomain_87fcae26-493d-45a5-80d5-0f651c97632f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_b9348ff5-a64c-4a89-885b-ba3cf8841766" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_87fcae26-493d-45a5-80d5-0f651c97632f" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_b9348ff5-a64c-4a89-885b-ba3cf8841766" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_595a9515-35ca-4db3-ab80-be2380150092" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_2f93f9e0-b933-409e-a317-8069d4b0ea0c" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_595a9515-35ca-4db3-ab80-be2380150092" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_595a9515-35ca-4db3-ab80-be2380150092_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_595a9515-35ca-4db3-ab80-be2380150092" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_595a9515-35ca-4db3-ab80-be2380150092_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_f0825683-ea60-4432-af45-42c76e2f4684" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_595a9515-35ca-4db3-ab80-be2380150092" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_f0825683-ea60-4432-af45-42c76e2f4684" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_54345430-e4a4-4750-b883-4f0b88c56bc0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_f0825683-ea60-4432-af45-42c76e2f4684" xlink:to="loc_us-gaap_LineOfCreditMember_54345430-e4a4-4750-b883-4f0b88c56bc0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_83eb4754-be35-4189-b7eb-b7f456449aba" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c0b79784-42ff-4de6-aa7f-7a79343b29eb" xlink:to="loc_us-gaap_LineOfCredit_83eb4754-be35-4189-b7eb-b7f456449aba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35ac99cb-19f4-4572-8518-ed1966aa1b39" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c0b79784-42ff-4de6-aa7f-7a79343b29eb" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35ac99cb-19f4-4572-8518-ed1966aa1b39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_MaximumIncrementalRevolvingCommitments_d53f1078-1295-4e7a-8001-647fca7aaaf0" xlink:href="pwp-20240630.xsd#pwp_MaximumIncrementalRevolvingCommitments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c0b79784-42ff-4de6-aa7f-7a79343b29eb" xlink:to="loc_pwp_MaximumIncrementalRevolvingCommitments_d53f1078-1295-4e7a-8001-647fca7aaaf0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_c35941e6-52c4-45aa-a10d-8e747d3078e9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c0b79784-42ff-4de6-aa7f-7a79343b29eb" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_c35941e6-52c4-45aa-a10d-8e747d3078e9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_ae944d75-f1a8-4a47-8e8b-93757e301adc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c0b79784-42ff-4de6-aa7f-7a79343b29eb" xlink:to="loc_us-gaap_InterestExpenseDebt_ae944d75-f1a8-4a47-8e8b-93757e301adc" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/EquityBasedCompensationAdditionalinformationDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#EquityBasedCompensationAdditionalinformationDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/EquityBasedCompensationAdditionalinformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_80ff68a7-9b83-47dc-abf6-7b5c32fc1d45" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_80ff68a7-9b83-47dc-abf6-7b5c32fc1d45" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_c34404d4-bca1-4f18-8ef0-169749ef12e2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_80ff68a7-9b83-47dc-abf6-7b5c32fc1d45" xlink:to="loc_us-gaap_AwardTypeAxis_c34404d4-bca1-4f18-8ef0-169749ef12e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c34404d4-bca1-4f18-8ef0-169749ef12e2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_c34404d4-bca1-4f18-8ef0-169749ef12e2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c34404d4-bca1-4f18-8ef0-169749ef12e2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_95877fab-2625-40f0-8abc-280e811ce765" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_c34404d4-bca1-4f18-8ef0-169749ef12e2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_95877fab-2625-40f0-8abc-280e811ce765" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_GeneralRsusMember_f88cdcc7-782d-4b7b-a281-ace28e3e4487" xlink:href="pwp-20240630.xsd#pwp_GeneralRsusMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_95877fab-2625-40f0-8abc-280e811ce765" xlink:to="loc_pwp_GeneralRsusMember_f88cdcc7-782d-4b7b-a281-ace28e3e4487" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_GeneralPSUsMember_56cb7258-59ee-49fd-b166-49517df8bf5f" xlink:href="pwp-20240630.xsd#pwp_GeneralPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_95877fab-2625-40f0-8abc-280e811ce765" xlink:to="loc_pwp_GeneralPSUsMember_56cb7258-59ee-49fd-b166-49517df8bf5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ProfessionalPartnersAwardMember_8bc7d1b5-1d6a-49e5-98e7-b72a7c9d9aba" xlink:href="pwp-20240630.xsd#pwp_ProfessionalPartnersAwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_95877fab-2625-40f0-8abc-280e811ce765" xlink:to="loc_pwp_ProfessionalPartnersAwardMember_8bc7d1b5-1d6a-49e5-98e7-b72a7c9d9aba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ProfessionalPartnersAwardsLiabilityClassifiedMember_4016fa20-71de-4906-a4b9-17748efbc9bd" xlink:href="pwp-20240630.xsd#pwp_ProfessionalPartnersAwardsLiabilityClassifiedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pwp_ProfessionalPartnersAwardMember_8bc7d1b5-1d6a-49e5-98e7-b72a7c9d9aba" xlink:to="loc_pwp_ProfessionalPartnersAwardsLiabilityClassifiedMember_4016fa20-71de-4906-a4b9-17748efbc9bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_GeneralAwardsMember_f3dd072d-17fa-4fbf-a808-1fbd474a65da" xlink:href="pwp-20240630.xsd#pwp_GeneralAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_95877fab-2625-40f0-8abc-280e811ce765" xlink:to="loc_pwp_GeneralAwardsMember_f3dd072d-17fa-4fbf-a808-1fbd474a65da" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TransactionPoolPsusMember_412907de-6db3-47bd-aad1-9909b1c7ec84" xlink:href="pwp-20240630.xsd#pwp_TransactionPoolPsusMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_95877fab-2625-40f0-8abc-280e811ce765" xlink:to="loc_pwp_TransactionPoolPsusMember_412907de-6db3-47bd-aad1-9909b1c7ec84" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_AlignmentCapitalUnitsLiabilityClassifiedMember_e29170a4-76d7-4028-960f-1e8f75a63270" xlink:href="pwp-20240630.xsd#pwp_AlignmentCapitalUnitsLiabilityClassifiedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_95877fab-2625-40f0-8abc-280e811ce765" xlink:to="loc_pwp_AlignmentCapitalUnitsLiabilityClassifiedMember_e29170a4-76d7-4028-960f-1e8f75a63270" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_df807dd4-c8dd-47d8-8b17-1fc216d7c4b8" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_80ff68a7-9b83-47dc-abf6-7b5c32fc1d45" xlink:to="loc_srt_RangeAxis_df807dd4-c8dd-47d8-8b17-1fc216d7c4b8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_df807dd4-c8dd-47d8-8b17-1fc216d7c4b8_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_df807dd4-c8dd-47d8-8b17-1fc216d7c4b8" xlink:to="loc_srt_RangeMember_df807dd4-c8dd-47d8-8b17-1fc216d7c4b8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_23c605bc-2486-47bc-ba64-7a13497f2df9" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_df807dd4-c8dd-47d8-8b17-1fc216d7c4b8" xlink:to="loc_srt_RangeMember_23c605bc-2486-47bc-ba64-7a13497f2df9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_0896d5b1-4090-4430-a0e2-b65f0883b637" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_23c605bc-2486-47bc-ba64-7a13497f2df9" xlink:to="loc_srt_MinimumMember_0896d5b1-4090-4430-a0e2-b65f0883b637" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_1ddb833f-1079-496b-9dca-61d3ae7d1c5f" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_23c605bc-2486-47bc-ba64-7a13497f2df9" xlink:to="loc_srt_MaximumMember_1ddb833f-1079-496b-9dca-61d3ae7d1c5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1c6ed446-a085-4bdb-ae77-5c779a0468b2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_80ff68a7-9b83-47dc-abf6-7b5c32fc1d45" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1c6ed446-a085-4bdb-ae77-5c779a0468b2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_1c6ed446-a085-4bdb-ae77-5c779a0468b2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1c6ed446-a085-4bdb-ae77-5c779a0468b2" xlink:to="loc_us-gaap_ClassOfStockDomain_1c6ed446-a085-4bdb-ae77-5c779a0468b2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_86abbfda-e52c-4162-af21-501add99d480" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1c6ed446-a085-4bdb-ae77-5c779a0468b2" xlink:to="loc_us-gaap_ClassOfStockDomain_86abbfda-e52c-4162-af21-501add99d480" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_698f2064-ae9d-4ae1-85d3-beb07d7246d3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_86abbfda-e52c-4162-af21-501add99d480" xlink:to="loc_us-gaap_CommonClassAMember_698f2064-ae9d-4ae1-85d3-beb07d7246d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_731f3634-d234-4ec8-8ac2-f3351c88daeb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_80ff68a7-9b83-47dc-abf6-7b5c32fc1d45" xlink:to="loc_us-gaap_PlanNameAxis_731f3634-d234-4ec8-8ac2-f3351c88daeb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_731f3634-d234-4ec8-8ac2-f3351c88daeb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_731f3634-d234-4ec8-8ac2-f3351c88daeb" xlink:to="loc_us-gaap_PlanNameDomain_731f3634-d234-4ec8-8ac2-f3351c88daeb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_5afeb6ff-4ab6-4f69-a44c-651aed7c21f4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_731f3634-d234-4ec8-8ac2-f3351c88daeb" xlink:to="loc_us-gaap_PlanNameDomain_5afeb6ff-4ab6-4f69-a44c-651aed7c21f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_VestingAccelerationMember_d4ad25e3-61b6-4fef-98aa-a0948c661dd2" xlink:href="pwp-20240630.xsd#pwp_VestingAccelerationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_5afeb6ff-4ab6-4f69-a44c-651aed7c21f4" xlink:to="loc_pwp_VestingAccelerationMember_d4ad25e3-61b6-4fef-98aa-a0948c661dd2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_d79bd522-5f3a-4f25-b792-ef98a2e2d3e9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_80ff68a7-9b83-47dc-abf6-7b5c32fc1d45" xlink:to="loc_us-gaap_VestingAxis_d79bd522-5f3a-4f25-b792-ef98a2e2d3e9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_d79bd522-5f3a-4f25-b792-ef98a2e2d3e9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_d79bd522-5f3a-4f25-b792-ef98a2e2d3e9" xlink:to="loc_us-gaap_VestingDomain_d79bd522-5f3a-4f25-b792-ef98a2e2d3e9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_b1ae8bfe-f559-4297-a361-accfd6e799b2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_d79bd522-5f3a-4f25-b792-ef98a2e2d3e9" xlink:to="loc_us-gaap_VestingDomain_b1ae8bfe-f559-4297-a361-accfd6e799b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_OneTwoPriceTrancheMember_3bb2cc64-d2b0-47bc-b485-714d93625557" xlink:href="pwp-20240630.xsd#pwp_OneTwoPriceTrancheMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_b1ae8bfe-f559-4297-a361-accfd6e799b2" xlink:to="loc_pwp_OneTwoPriceTrancheMember_3bb2cc64-d2b0-47bc-b485-714d93625557" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_OneFivePriceTrancheMember_09ac2703-b2fa-401d-9d5a-79b6f4bc844c" xlink:href="pwp-20240630.xsd#pwp_OneFivePriceTrancheMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_b1ae8bfe-f559-4297-a361-accfd6e799b2" xlink:to="loc_pwp_OneFivePriceTrancheMember_09ac2703-b2fa-401d-9d5a-79b6f4bc844c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_OneThreePointFiveZeroPriceTrancheMember_87c2dd2c-e3f8-4013-8a28-f9420342cc8d" xlink:href="pwp-20240630.xsd#pwp_OneThreePointFiveZeroPriceTrancheMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_b1ae8bfe-f559-4297-a361-accfd6e799b2" xlink:to="loc_pwp_OneThreePointFiveZeroPriceTrancheMember_87c2dd2c-e3f8-4013-8a28-f9420342cc8d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_MarketConditionSharePriceAchieved_9e9beec0-08fc-483a-b171-7e0f7ef983b1" xlink:href="pwp-20240630.xsd#pwp_MarketConditionSharePriceAchieved"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_pwp_MarketConditionSharePriceAchieved_9e9beec0-08fc-483a-b171-7e0f7ef983b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_53f24e0c-9b0e-4a6c-871e-43a3a8e02922" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_53f24e0c-9b0e-4a6c-871e-43a3a8e02922" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_d4181ee0-86d8-4750-88fa-afce0e038099" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_d4181ee0-86d8-4750-88fa-afce0e038099" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_09e1f081-a00e-4b6b-b526-1e13f443ac95" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_09e1f081-a00e-4b6b-b526-1e13f443ac95" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_65d6786c-e8a9-446c-9154-d3ee93ad565a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_65d6786c-e8a9-446c-9154-d3ee93ad565a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_9158d630-f5c9-4fd0-afae-c64196519a9f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_9158d630-f5c9-4fd0-afae-c64196519a9f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost_29ec2c67-8f65-4acf-ad90-a91d400f7a8f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost_29ec2c67-8f65-4acf-ad90-a91d400f7a8f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAcceleratedVestingNumber_344f8ebc-aff7-4e03-885c-e3a71a4fe915" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAcceleratedVestingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAcceleratedVestingNumber_344f8ebc-aff7-4e03-885c-e3a71a4fe915" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedVestingSettlement_451157d9-eade-456a-9412-fd0320c9f20d" xlink:href="pwp-20240630.xsd#pwp_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedVestingSettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_pwp_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedVestingSettlement_451157d9-eade-456a-9412-fd0320c9f20d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_6b52c45a-8751-4781-a910-c8ae9fde8461" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_ShareBasedCompensation_6b52c45a-8751-4781-a910-c8ae9fde8461" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_d1ec16b0-772d-4fc4-99b8-ca4510cabcb0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_d1ec16b0-772d-4fc4-99b8-ca4510cabcb0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_67a33281-8cde-44c2-adab-de18c888a1de" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_67a33281-8cde-44c2-adab-de18c888a1de" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_17f00697-5049-4c83-8733-48b15d29e713" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_17f00697-5049-4c83-8733-48b15d29e713" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_9839bbe7-410b-4159-8873-c71f5ecac601" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53e46ea6-fc28-4066-a291-23183175b95c" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_9839bbe7-410b-4159-8873-c71f5ecac601" xlink:type="arc" order="13"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/EquityBasedCompensationSummaryofAwardsExpenseDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#EquityBasedCompensationSummaryofAwardsExpenseDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/EquityBasedCompensationSummaryofAwardsExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_fd9892fe-9047-402d-98b1-c709f43e794b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_371a5f92-ded0-4ac3-89cd-67327711bd52" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_fd9892fe-9047-402d-98b1-c709f43e794b" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_371a5f92-ded0-4ac3-89cd-67327711bd52" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_636fca35-58bd-495b-8961-1a6ddcc677f8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_371a5f92-ded0-4ac3-89cd-67327711bd52" xlink:to="loc_us-gaap_AwardTypeAxis_636fca35-58bd-495b-8961-1a6ddcc677f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_636fca35-58bd-495b-8961-1a6ddcc677f8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_636fca35-58bd-495b-8961-1a6ddcc677f8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_636fca35-58bd-495b-8961-1a6ddcc677f8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ffd1f8ec-d9e1-4fd4-9949-fac8f9110f16" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_636fca35-58bd-495b-8961-1a6ddcc677f8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ffd1f8ec-d9e1-4fd4-9949-fac8f9110f16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_IncentivePlanAwardsMember_4f55441b-b8d9-46a9-956e-7c05b6bc9bb5" xlink:href="pwp-20240630.xsd#pwp_IncentivePlanAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ffd1f8ec-d9e1-4fd4-9949-fac8f9110f16" xlink:to="loc_pwp_IncentivePlanAwardsMember_4f55441b-b8d9-46a9-956e-7c05b6bc9bb5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_LegacyAwardsMember_cb509a5c-a89c-4dde-a808-55330ab6361f" xlink:href="pwp-20240630.xsd#pwp_LegacyAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ffd1f8ec-d9e1-4fd4-9949-fac8f9110f16" xlink:to="loc_pwp_LegacyAwardsMember_cb509a5c-a89c-4dde-a808-55330ab6361f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ProfessionalPartnersAwardEquityClassifiedMember_926e9d27-a2a4-4b16-b5f6-7c44101f24ce" xlink:href="pwp-20240630.xsd#pwp_ProfessionalPartnersAwardEquityClassifiedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ffd1f8ec-d9e1-4fd4-9949-fac8f9110f16" xlink:to="loc_pwp_ProfessionalPartnersAwardEquityClassifiedMember_926e9d27-a2a4-4b16-b5f6-7c44101f24ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ProfessionalPartnersAwardsLiabilityClassifiedMember_bbf9d962-b4ef-43ac-b9fa-58029474ffe6" xlink:href="pwp-20240630.xsd#pwp_ProfessionalPartnersAwardsLiabilityClassifiedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ffd1f8ec-d9e1-4fd4-9949-fac8f9110f16" xlink:to="loc_pwp_ProfessionalPartnersAwardsLiabilityClassifiedMember_bbf9d962-b4ef-43ac-b9fa-58029474ffe6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ProfessionalPartnersAwardMember_213f4c1e-7539-41ff-954a-139ee1351fe9" xlink:href="pwp-20240630.xsd#pwp_ProfessionalPartnersAwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ffd1f8ec-d9e1-4fd4-9949-fac8f9110f16" xlink:to="loc_pwp_ProfessionalPartnersAwardMember_213f4c1e-7539-41ff-954a-139ee1351fe9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_b65f7799-4fe7-4007-a95f-7454a4dc8954" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_fd9892fe-9047-402d-98b1-c709f43e794b" xlink:to="loc_us-gaap_ProfessionalFees_b65f7799-4fe7-4007-a95f-7454a4dc8954" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_9ed058b0-b968-4d62-9464-11d17fd544e6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_fd9892fe-9047-402d-98b1-c709f43e794b" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_9ed058b0-b968-4d62-9464-11d17fd544e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_b60e2787-2623-42a4-8cc5-bf11a20913c6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_fd9892fe-9047-402d-98b1-c709f43e794b" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_b60e2787-2623-42a4-8cc5-bf11a20913c6" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/OtherCompensationandBenefitsAdditionalInformationDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#OtherCompensationandBenefitsAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/OtherCompensationandBenefitsAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_43aa9d5c-686f-4aa5-a4e5-87b69d6fcf76" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_2cac6c09-576f-4963-805f-7e0cc31c7837" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_43aa9d5c-686f-4aa5-a4e5-87b69d6fcf76" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_2cac6c09-576f-4963-805f-7e0cc31c7837" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanNameAxis_ac3c4b7a-f724-4860-94c2-02a6109996bb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetirementPlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_2cac6c09-576f-4963-805f-7e0cc31c7837" xlink:to="loc_us-gaap_RetirementPlanNameAxis_ac3c4b7a-f724-4860-94c2-02a6109996bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanNameDomain_ac3c4b7a-f724-4860-94c2-02a6109996bb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetirementPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanNameAxis_ac3c4b7a-f724-4860-94c2-02a6109996bb" xlink:to="loc_us-gaap_RetirementPlanNameDomain_ac3c4b7a-f724-4860-94c2-02a6109996bb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanNameDomain_7aa1cd95-21ff-4c59-9789-f16930945a68" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetirementPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanNameAxis_ac3c4b7a-f724-4860-94c2-02a6109996bb" xlink:to="loc_us-gaap_RetirementPlanNameDomain_7aa1cd95-21ff-4c59-9789-f16930945a68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_BusinessRealignmentMember_8fd5e960-b75b-4323-9de0-6916b97e2cf6" xlink:href="pwp-20240630.xsd#pwp_BusinessRealignmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanNameDomain_7aa1cd95-21ff-4c59-9789-f16930945a68" xlink:to="loc_pwp_BusinessRealignmentMember_8fd5e960-b75b-4323-9de0-6916b97e2cf6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_6dca0ce6-7d7c-4d56-9f63-2517ffc6db65" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_2cac6c09-576f-4963-805f-7e0cc31c7837" xlink:to="loc_us-gaap_RestructuringPlanAxis_6dca0ce6-7d7c-4d56-9f63-2517ffc6db65" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_6dca0ce6-7d7c-4d56-9f63-2517ffc6db65_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_6dca0ce6-7d7c-4d56-9f63-2517ffc6db65" xlink:to="loc_us-gaap_RestructuringPlanDomain_6dca0ce6-7d7c-4d56-9f63-2517ffc6db65_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_3d88131f-28f6-4cf7-91a6-759facb36bf9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_6dca0ce6-7d7c-4d56-9f63-2517ffc6db65" xlink:to="loc_us-gaap_RestructuringPlanDomain_3d88131f-28f6-4cf7-91a6-759facb36bf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_BusinessRealignmentMember_5aa7af12-702a-4608-9c83-f843a0c1d558" xlink:href="pwp-20240630.xsd#pwp_BusinessRealignmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_3d88131f-28f6-4cf7-91a6-759facb36bf9" xlink:to="loc_pwp_BusinessRealignmentMember_5aa7af12-702a-4608-9c83-f843a0c1d558" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_AcceleratedShareBasedCompensationMember_9182635b-e3ed-4a11-a2c3-9308096e3e50" xlink:href="pwp-20240630.xsd#pwp_AcceleratedShareBasedCompensationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_3d88131f-28f6-4cf7-91a6-759facb36bf9" xlink:to="loc_pwp_AcceleratedShareBasedCompensationMember_9182635b-e3ed-4a11-a2c3-9308096e3e50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_eddf7ba6-2f41-4b5e-9734-90bcbc16a0a1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_2cac6c09-576f-4963-805f-7e0cc31c7837" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_eddf7ba6-2f41-4b5e-9734-90bcbc16a0a1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_eddf7ba6-2f41-4b5e-9734-90bcbc16a0a1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_eddf7ba6-2f41-4b5e-9734-90bcbc16a0a1" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_eddf7ba6-2f41-4b5e-9734-90bcbc16a0a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_00f5061c-8e86-437e-8826-f3333108a089" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_eddf7ba6-2f41-4b5e-9734-90bcbc16a0a1" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_00f5061c-8e86-437e-8826-f3333108a089" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_576605f3-6659-4b22-93ff-e14616c8e30a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_00f5061c-8e86-437e-8826-f3333108a089" xlink:to="loc_us-gaap_EmployeeSeveranceMember_576605f3-6659-4b22-93ff-e14616c8e30a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanCostRecognized_162c8d9e-7eeb-47ce-9ef7-bac0f5475962" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DefinedContributionPlanCostRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_43aa9d5c-686f-4aa5-a4e5-87b69d6fcf76" xlink:to="loc_us-gaap_DefinedContributionPlanCostRecognized_162c8d9e-7eeb-47ce-9ef7-bac0f5475962" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostIncurredCost_be391923-37cc-4b5a-9979-6d16ce0dbab9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringAndRelatedCostIncurredCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_43aa9d5c-686f-4aa5-a4e5-87b69d6fcf76" xlink:to="loc_us-gaap_RestructuringAndRelatedCostIncurredCost_be391923-37cc-4b5a-9979-6d16ce0dbab9" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/OtherCompensationandBenefitsRestructuringandRelatedCostsDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#OtherCompensationandBenefitsRestructuringandRelatedCostsDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/OtherCompensationandBenefitsRestructuringandRelatedCostsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_7253455e-f726-471c-ac02-efa9bbf024e4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_27f881fb-1b92-4893-a8dc-1f4127e0ae93" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_7253455e-f726-471c-ac02-efa9bbf024e4" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_27f881fb-1b92-4893-a8dc-1f4127e0ae93" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_3562d58c-d389-4622-9743-99224c09295d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_27f881fb-1b92-4893-a8dc-1f4127e0ae93" xlink:to="loc_us-gaap_RestructuringPlanAxis_3562d58c-d389-4622-9743-99224c09295d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_3562d58c-d389-4622-9743-99224c09295d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_3562d58c-d389-4622-9743-99224c09295d" xlink:to="loc_us-gaap_RestructuringPlanDomain_3562d58c-d389-4622-9743-99224c09295d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_49f7c8f7-5df4-45cd-8403-330ee4c89c91" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_3562d58c-d389-4622-9743-99224c09295d" xlink:to="loc_us-gaap_RestructuringPlanDomain_49f7c8f7-5df4-45cd-8403-330ee4c89c91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_BusinessRealignmentMember_f3762d2a-323b-482f-bb93-2061a3cbc150" xlink:href="pwp-20240630.xsd#pwp_BusinessRealignmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_49f7c8f7-5df4-45cd-8403-330ee4c89c91" xlink:to="loc_pwp_BusinessRealignmentMember_f3762d2a-323b-482f-bb93-2061a3cbc150" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveRollForward_ed668f9b-3fda-4246-9580-b087187ecf4d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringReserveRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_7253455e-f726-471c-ac02-efa9bbf024e4" xlink:to="loc_us-gaap_RestructuringReserveRollForward_ed668f9b-3fda-4246-9580-b087187ecf4d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_a0f32534-154c-4cbc-977b-0f2649022e04" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_ed668f9b-3fda-4246-9580-b087187ecf4d" xlink:to="loc_us-gaap_RestructuringReserve_a0f32534-154c-4cbc-977b-0f2649022e04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostIncurredCost_61b3b89c-f2ee-466c-8971-710de1693e26" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringAndRelatedCostIncurredCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_ed668f9b-3fda-4246-9580-b087187ecf4d" xlink:to="loc_us-gaap_RestructuringAndRelatedCostIncurredCost_61b3b89c-f2ee-466c-8971-710de1693e26" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveSettledWithoutCash2_2429ba69-a2ae-48f5-aeb3-5275b2a12b3a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringReserveSettledWithoutCash2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_ed668f9b-3fda-4246-9580-b087187ecf4d" xlink:to="loc_us-gaap_RestructuringReserveSettledWithoutCash2_2429ba69-a2ae-48f5-aeb3-5275b2a12b3a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRestructuring_a4bac8ec-dc60-4e48-9bee-14d978952c2a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsForRestructuring"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_ed668f9b-3fda-4246-9580-b087187ecf4d" xlink:to="loc_us-gaap_PaymentsForRestructuring_a4bac8ec-dc60-4e48-9bee-14d978952c2a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_ed15eff8-4412-44e7-8763-71978ff205d0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringReserve"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/NetIncomeLossPerShareAttributabletoClassACommonShareholdersScheduleofWeightedAveragePotentiallyDilutiveSharesExcludedfromComputationofDilutedNetIncomeLossPerShareDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#NetIncomeLossPerShareAttributabletoClassACommonShareholdersScheduleofWeightedAveragePotentiallyDilutiveSharesExcludedfromComputationofDilutedNetIncomeLossPerShareDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/NetIncomeLossPerShareAttributabletoClassACommonShareholdersScheduleofWeightedAveragePotentiallyDilutiveSharesExcludedfromComputationofDilutedNetIncomeLossPerShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_26732cb2-742a-4874-adf1-13e2bdcd1e6b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_bc54bdf9-fc0d-451a-944b-2bb9f865ae1e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_26732cb2-742a-4874-adf1-13e2bdcd1e6b" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_bc54bdf9-fc0d-451a-944b-2bb9f865ae1e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_755abc7a-54fd-42fd-a7e7-5524cd62d357" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_bc54bdf9-fc0d-451a-944b-2bb9f865ae1e" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_755abc7a-54fd-42fd-a7e7-5524cd62d357" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_755abc7a-54fd-42fd-a7e7-5524cd62d357_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_755abc7a-54fd-42fd-a7e7-5524cd62d357" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_755abc7a-54fd-42fd-a7e7-5524cd62d357_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7316234b-31c2-4ed6-947d-6236596c9aff" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_755abc7a-54fd-42fd-a7e7-5524cd62d357" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7316234b-31c2-4ed6-947d-6236596c9aff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_PWPOpCoClassAPartnershipUnitsMember_303d709f-6e30-4722-9791-e9cd863d0d5e" xlink:href="pwp-20240630.xsd#pwp_PWPOpCoClassAPartnershipUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7316234b-31c2-4ed6-947d-6236596c9aff" xlink:to="loc_pwp_PWPOpCoClassAPartnershipUnitsMember_303d709f-6e30-4722-9791-e9cd863d0d5e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_IncentivePlanAwardsMember_be2a2ec4-5a01-4394-84dc-1dd79f1ca818" xlink:href="pwp-20240630.xsd#pwp_IncentivePlanAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7316234b-31c2-4ed6-947d-6236596c9aff" xlink:to="loc_pwp_IncentivePlanAwardsMember_be2a2ec4-5a01-4394-84dc-1dd79f1ca818" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_2b891f7c-4607-40b3-bcbe-402f3d58787c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_26732cb2-742a-4874-adf1-13e2bdcd1e6b" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_2b891f7c-4607-40b3-bcbe-402f3d58787c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/FairValueMeasurementsandInvestmentsScheduleofAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#FairValueMeasurementsandInvestmentsScheduleofAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/FairValueMeasurementsandInvestmentsScheduleofAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_69101db1-4949-4681-849a-a8c76cbaadad" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_0aad087a-60ca-42b9-8605-65b7d90375a8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_69101db1-4949-4681-849a-a8c76cbaadad" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_0aad087a-60ca-42b9-8605-65b7d90375a8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_06c2e291-ebce-428f-8974-c55efd407a2a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_0aad087a-60ca-42b9-8605-65b7d90375a8" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_06c2e291-ebce-428f-8974-c55efd407a2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_06c2e291-ebce-428f-8974-c55efd407a2a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_06c2e291-ebce-428f-8974-c55efd407a2a" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_06c2e291-ebce-428f-8974-c55efd407a2a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_74e484e7-ebea-403f-b87c-962e91a4b771" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_06c2e291-ebce-428f-8974-c55efd407a2a" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_74e484e7-ebea-403f-b87c-962e91a4b771" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_2f5fe534-046c-4079-b598-884298f0893b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_74e484e7-ebea-403f-b87c-962e91a4b771" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_2f5fe534-046c-4079-b598-884298f0893b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_1524fad4-53f5-4f27-a5db-b89561109e3e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_0aad087a-60ca-42b9-8605-65b7d90375a8" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_1524fad4-53f5-4f27-a5db-b89561109e3e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1524fad4-53f5-4f27-a5db-b89561109e3e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_1524fad4-53f5-4f27-a5db-b89561109e3e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1524fad4-53f5-4f27-a5db-b89561109e3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4f1497e3-4d21-4b4c-a575-6ae5105017b6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_1524fad4-53f5-4f27-a5db-b89561109e3e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4f1497e3-4d21-4b4c-a575-6ae5105017b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_b51c66bc-f7f5-4316-8a92-c20e6415139e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4f1497e3-4d21-4b4c-a575-6ae5105017b6" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_b51c66bc-f7f5-4316-8a92-c20e6415139e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_8031e046-9f54-473a-b316-325daeaee557" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4f1497e3-4d21-4b4c-a575-6ae5105017b6" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_8031e046-9f54-473a-b316-325daeaee557" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_d79c233a-1054-4a36-b7cc-e064ff0bf073" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4f1497e3-4d21-4b4c-a575-6ae5105017b6" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_d79c233a-1054-4a36-b7cc-e064ff0bf073" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_FinancialAssetsFairValueDisclosureAbstract_6978b09c-b1e8-426f-a748-7e4fcf2a9cb5" xlink:href="pwp-20240630.xsd#pwp_FinancialAssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_69101db1-4949-4681-849a-a8c76cbaadad" xlink:to="loc_pwp_FinancialAssetsFairValueDisclosureAbstract_6978b09c-b1e8-426f-a748-7e4fcf2a9cb5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_ba699691-1755-4f9c-9160-e155762cf654" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pwp_FinancialAssetsFairValueDisclosureAbstract_6978b09c-b1e8-426f-a748-7e4fcf2a9cb5" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_ba699691-1755-4f9c-9160-e155762cf654" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/RelatedPartyTransactionsAdditionalInformationDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#RelatedPartyTransactionsAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/RelatedPartyTransactionsAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_4b2ffad8-f255-4a22-85c2-aeee4d69e945" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8e2d4f5b-9ca5-4129-9be8-e072e9d47ac4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_4b2ffad8-f255-4a22-85c2-aeee4d69e945" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8e2d4f5b-9ca5-4129-9be8-e072e9d47ac4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0b850618-8954-4d32-942f-14b285d96fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8e2d4f5b-9ca5-4129-9be8-e072e9d47ac4" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0b850618-8954-4d32-942f-14b285d96fe9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_0b850618-8954-4d32-942f-14b285d96fe9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0b850618-8954-4d32-942f-14b285d96fe9" xlink:to="loc_us-gaap_RelatedPartyDomain_0b850618-8954-4d32-942f-14b285d96fe9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_50e379f3-1f04-4539-8047-8dc64ecf32f2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0b850618-8954-4d32-942f-14b285d96fe9" xlink:to="loc_us-gaap_RelatedPartyDomain_50e379f3-1f04-4539-8047-8dc64ecf32f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_PartnersMember_870fd430-c562-452a-899a-443b306dfb02" xlink:href="pwp-20240630.xsd#pwp_PartnersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_50e379f3-1f04-4539-8047-8dc64ecf32f2" xlink:to="loc_pwp_PartnersMember_870fd430-c562-452a-899a-443b306dfb02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TaxReceivableAgreementTaxSavingsPercentage_1366d81a-f67c-4162-b813-60b69818d786" xlink:href="pwp-20240630.xsd#pwp_TaxReceivableAgreementTaxSavingsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_4b2ffad8-f255-4a22-85c2-aeee4d69e945" xlink:to="loc_pwp_TaxReceivableAgreementTaxSavingsPercentage_1366d81a-f67c-4162-b813-60b69818d786" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_AmountDuePursuantToTaxReceivableAgreement_0e7f6514-6168-4f2c-8a3c-68723626f46c" xlink:href="pwp-20240630.xsd#pwp_AmountDuePursuantToTaxReceivableAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_4b2ffad8-f255-4a22-85c2-aeee4d69e945" xlink:to="loc_pwp_AmountDuePursuantToTaxReceivableAgreement_0e7f6514-6168-4f2c-8a3c-68723626f46c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_RelatedPartyTransactionPartnerPromissoryNotes_d90c27eb-2b24-4e83-b897-46a282ade680" xlink:href="pwp-20240630.xsd#pwp_RelatedPartyTransactionPartnerPromissoryNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_4b2ffad8-f255-4a22-85c2-aeee4d69e945" xlink:to="loc_pwp_RelatedPartyTransactionPartnerPromissoryNotes_d90c27eb-2b24-4e83-b897-46a282ade680" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivablesNetCurrent_ae3fde8d-91b8-4009-a1dc-cfc3f845e4d0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherReceivablesNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_4b2ffad8-f255-4a22-85c2-aeee4d69e945" xlink:to="loc_us-gaap_OtherReceivablesNetCurrent_ae3fde8d-91b8-4009-a1dc-cfc3f845e4d0" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/CommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#CommitmentsandContingenciesDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/CommitmentsandContingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_61432329-42f6-40cc-982c-7fd14c6c1fb1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_2570ad04-c141-4c40-9253-7abfc4d45316" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_61432329-42f6-40cc-982c-7fd14c6c1fb1" xlink:to="loc_us-gaap_LossContingenciesTable_2570ad04-c141-4c40-9253-7abfc4d45316" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_721c02c6-8398-4368-bcb1-fa1148c7b6fa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_2570ad04-c141-4c40-9253-7abfc4d45316" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_721c02c6-8398-4368-bcb1-fa1148c7b6fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_721c02c6-8398-4368-bcb1-fa1148c7b6fa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_721c02c6-8398-4368-bcb1-fa1148c7b6fa" xlink:to="loc_us-gaap_LossContingencyNatureDomain_721c02c6-8398-4368-bcb1-fa1148c7b6fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_421cd6af-8a8c-41b9-97f3-e08cc4ffd16f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_721c02c6-8398-4368-bcb1-fa1148c7b6fa" xlink:to="loc_us-gaap_LossContingencyNatureDomain_421cd6af-8a8c-41b9-97f3-e08cc4ffd16f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndemnificationGuaranteeMember_11c603a4-9a4e-410b-b789-6b40bd97f113" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndemnificationGuaranteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_421cd6af-8a8c-41b9-97f3-e08cc4ffd16f" xlink:to="loc_us-gaap_IndemnificationGuaranteeMember_11c603a4-9a4e-410b-b789-6b40bd97f113" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusAxis_ca822b5c-2b83-46a9-8c7d-029119a8ee5c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_2570ad04-c141-4c40-9253-7abfc4d45316" xlink:to="loc_us-gaap_LitigationStatusAxis_ca822b5c-2b83-46a9-8c7d-029119a8ee5c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_ca822b5c-2b83-46a9-8c7d-029119a8ee5c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_ca822b5c-2b83-46a9-8c7d-029119a8ee5c" xlink:to="loc_us-gaap_LitigationStatusDomain_ca822b5c-2b83-46a9-8c7d-029119a8ee5c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_1eba7bdd-0eaf-4f8a-8f27-376ad58f6bce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_ca822b5c-2b83-46a9-8c7d-029119a8ee5c" xlink:to="loc_us-gaap_LitigationStatusDomain_1eba7bdd-0eaf-4f8a-8f27-376ad58f6bce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PendingLitigationMember_4cc56b9e-cc91-48fa-a107-83a3ed0845fc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PendingLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_1eba7bdd-0eaf-4f8a-8f27-376ad58f6bce" xlink:to="loc_us-gaap_PendingLitigationMember_4cc56b9e-cc91-48fa-a107-83a3ed0845fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_d6de0e59-3ff4-4cab-b803-2bf321d51ae8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingencyEstimateOfPossibleLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_61432329-42f6-40cc-982c-7fd14c6c1fb1" xlink:to="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_d6de0e59-3ff4-4cab-b803-2bf321d51ae8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_NumberOfFormerPartners_547ceb42-bc3b-4146-95bb-6702f0b8da66" xlink:href="pwp-20240630.xsd#pwp_NumberOfFormerPartners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_61432329-42f6-40cc-982c-7fd14c6c1fb1" xlink:to="loc_pwp_NumberOfFormerPartners_547ceb42-bc3b-4146-95bb-6702f0b8da66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_NumberOfFormerEmployees_96749e61-9fa3-490b-9bae-67e780bf97d2" xlink:href="pwp-20240630.xsd#pwp_NumberOfFormerEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_61432329-42f6-40cc-982c-7fd14c6c1fb1" xlink:to="loc_pwp_NumberOfFormerEmployees_96749e61-9fa3-490b-9bae-67e780bf97d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_LossContingencyPendingPlaintiffsClaimsNumber_2b062e76-5795-4936-be4d-33038783264f" xlink:href="pwp-20240630.xsd#pwp_LossContingencyPendingPlaintiffsClaimsNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_61432329-42f6-40cc-982c-7fd14c6c1fb1" xlink:to="loc_pwp_LossContingencyPendingPlaintiffsClaimsNumber_2b062e76-5795-4936-be4d-33038783264f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementExpense_cb3fcbd2-3538-4cec-a4f2-dd6106fac1ff" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationSettlementExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_61432329-42f6-40cc-982c-7fd14c6c1fb1" xlink:to="loc_us-gaap_LitigationSettlementExpense_cb3fcbd2-3538-4cec-a4f2-dd6106fac1ff" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/BusinessInformationAdditionalInformationDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#BusinessInformationAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/BusinessInformationAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_a96194f8-4094-4a38-95a9-dfeaac3a4ac8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_b6fcdd47-6cc2-4dbb-ac73-e01923429a9a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a96194f8-4094-4a38-95a9-dfeaac3a4ac8" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_b6fcdd47-6cc2-4dbb-ac73-e01923429a9a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_b749bed3-83df-4f4b-96d0-e31cc0cebf46" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_b6fcdd47-6cc2-4dbb-ac73-e01923429a9a" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_b749bed3-83df-4f4b-96d0-e31cc0cebf46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_b749bed3-83df-4f4b-96d0-e31cc0cebf46_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_b749bed3-83df-4f4b-96d0-e31cc0cebf46" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_b749bed3-83df-4f4b-96d0-e31cc0cebf46_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_241c85fa-78df-4fe2-92bf-b06ae3fc73ea" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_b749bed3-83df-4f4b-96d0-e31cc0cebf46" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_241c85fa-78df-4fe2-92bf-b06ae3fc73ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_4031e269-fed7-4b27-a865-0347d8252cd9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_241c85fa-78df-4fe2-92bf-b06ae3fc73ea" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_4031e269-fed7-4b27-a865-0347d8252cd9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_45dc16d3-2c23-4eb4-bf4d-30827b7658b3" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_b6fcdd47-6cc2-4dbb-ac73-e01923429a9a" xlink:to="loc_srt_MajorCustomersAxis_45dc16d3-2c23-4eb4-bf4d-30827b7658b3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_45dc16d3-2c23-4eb4-bf4d-30827b7658b3_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_45dc16d3-2c23-4eb4-bf4d-30827b7658b3" xlink:to="loc_srt_NameOfMajorCustomerDomain_45dc16d3-2c23-4eb4-bf4d-30827b7658b3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_5bb28fcb-7e76-4200-b0f0-20b5df5bb3f8" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_45dc16d3-2c23-4eb4-bf4d-30827b7658b3" xlink:to="loc_srt_NameOfMajorCustomerDomain_5bb28fcb-7e76-4200-b0f0-20b5df5bb3f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_OneCustomerMember_d0b7f162-d0c8-4f60-8e30-65091725af78" xlink:href="pwp-20240630.xsd#pwp_OneCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_5bb28fcb-7e76-4200-b0f0-20b5df5bb3f8" xlink:to="loc_pwp_OneCustomerMember_d0b7f162-d0c8-4f60-8e30-65091725af78" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TwoCustomersMember_fe52405e-34c8-4c20-bbbd-bd6dce5f4b2a" xlink:href="pwp-20240630.xsd#pwp_TwoCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_5bb28fcb-7e76-4200-b0f0-20b5df5bb3f8" xlink:to="loc_pwp_TwoCustomersMember_fe52405e-34c8-4c20-bbbd-bd6dce5f4b2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_b5a385a8-4ca3-4181-9c5a-69af5200f7bb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_b6fcdd47-6cc2-4dbb-ac73-e01923429a9a" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_b5a385a8-4ca3-4181-9c5a-69af5200f7bb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b5a385a8-4ca3-4181-9c5a-69af5200f7bb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_b5a385a8-4ca3-4181-9c5a-69af5200f7bb" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b5a385a8-4ca3-4181-9c5a-69af5200f7bb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_efc9f15b-9098-456e-93f4-c548401f475e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_b5a385a8-4ca3-4181-9c5a-69af5200f7bb" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_efc9f15b-9098-456e-93f4-c548401f475e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_e8aa5212-52f4-4190-bd23-bbe069611942" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_efc9f15b-9098-456e-93f4-c548401f475e" xlink:to="loc_us-gaap_SalesRevenueNetMember_e8aa5212-52f4-4190-bd23-bbe069611942" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfOperatingSegments_28981306-1584-4609-bc55-f3f2fe326dee" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NumberOfOperatingSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a96194f8-4094-4a38-95a9-dfeaac3a4ac8" xlink:to="loc_us-gaap_NumberOfOperatingSegments_28981306-1584-4609-bc55-f3f2fe326dee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_aac7cdb9-21c2-4daf-8bc9-662df2a3a584" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a96194f8-4094-4a38-95a9-dfeaac3a4ac8" xlink:to="loc_us-gaap_NumberOfReportableSegments_aac7cdb9-21c2-4daf-8bc9-662df2a3a584" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_f614699e-08e7-4ab8-9c00-98f34d31a4c6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a96194f8-4094-4a38-95a9-dfeaac3a4ac8" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_f614699e-08e7-4ab8-9c00-98f34d31a4c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_7b4413a0-1391-4c9f-bfc2-444175ffb4a6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a96194f8-4094-4a38-95a9-dfeaac3a4ac8" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_7b4413a0-1391-4c9f-bfc2-444175ffb4a6" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/BusinessInformationScheduleofGeographicalDistributionofRevenuesandAssetsDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#BusinessInformationScheduleofGeographicalDistributionofRevenuesandAssetsDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/BusinessInformationScheduleofGeographicalDistributionofRevenuesandAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_183a62a9-c721-440f-bb9c-34185b717113" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_d5f7c498-9bf1-49cc-ab20-dc2a0c2982b7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_183a62a9-c721-440f-bb9c-34185b717113" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_d5f7c498-9bf1-49cc-ab20-dc2a0c2982b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_265cf06d-aeb6-413b-a2e3-b94e221dc91b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_d5f7c498-9bf1-49cc-ab20-dc2a0c2982b7" xlink:to="loc_srt_StatementGeographicalAxis_265cf06d-aeb6-413b-a2e3-b94e221dc91b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_265cf06d-aeb6-413b-a2e3-b94e221dc91b_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_265cf06d-aeb6-413b-a2e3-b94e221dc91b" xlink:to="loc_srt_SegmentGeographicalDomain_265cf06d-aeb6-413b-a2e3-b94e221dc91b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_ece67e1c-7f5f-47b1-8811-116fd371804f" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_265cf06d-aeb6-413b-a2e3-b94e221dc91b" xlink:to="loc_srt_SegmentGeographicalDomain_ece67e1c-7f5f-47b1-8811-116fd371804f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_761968e4-f2e8-4825-8122-f5efbf1768ff" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_ece67e1c-7f5f-47b1-8811-116fd371804f" xlink:to="loc_country_US_761968e4-f2e8-4825-8122-f5efbf1768ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_e84fd1d9-2b67-490e-9fea-a87c6b6ffcab" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_ece67e1c-7f5f-47b1-8811-116fd371804f" xlink:to="loc_us-gaap_NonUsMember_e84fd1d9-2b67-490e-9fea-a87c6b6ffcab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_cabb622b-74dc-4005-8114-2da010f5150a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_183a62a9-c721-440f-bb9c-34185b717113" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_cabb622b-74dc-4005-8114-2da010f5150a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_3dd43a7a-8b36-4ace-a815-69b7bb54de02" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_183a62a9-c721-440f-bb9c-34185b717113" xlink:to="loc_us-gaap_Assets_3dd43a7a-8b36-4ace-a815-69b7bb54de02" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://pwp.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="pwp-20240630.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://pwp.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_b42de66b-016d-4c66-8630-06b1af0aefba" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_04cd1e32-cf55-4d3a-a5f8-43200b19b838" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_b42de66b-016d-4c66-8630-06b1af0aefba" xlink:to="loc_us-gaap_SubsequentEventTable_04cd1e32-cf55-4d3a-a5f8-43200b19b838" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_0442ca7a-8a30-4a05-9ad9-2bcd499a29d7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_04cd1e32-cf55-4d3a-a5f8-43200b19b838" xlink:to="loc_us-gaap_StatementClassOfStockAxis_0442ca7a-8a30-4a05-9ad9-2bcd499a29d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_0442ca7a-8a30-4a05-9ad9-2bcd499a29d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_0442ca7a-8a30-4a05-9ad9-2bcd499a29d7" xlink:to="loc_us-gaap_ClassOfStockDomain_0442ca7a-8a30-4a05-9ad9-2bcd499a29d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_71fcdd30-e8af-4fe3-a0d0-7ba8022bcba1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_0442ca7a-8a30-4a05-9ad9-2bcd499a29d7" xlink:to="loc_us-gaap_ClassOfStockDomain_71fcdd30-e8af-4fe3-a0d0-7ba8022bcba1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_edb0425d-06ef-41ae-a3ad-727c6253bcd0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_71fcdd30-e8af-4fe3-a0d0-7ba8022bcba1" xlink:to="loc_us-gaap_CommonClassAMember_edb0425d-06ef-41ae-a3ad-727c6253bcd0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_2a1392f7-5a81-4b23-a89c-532d0faae72e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_71fcdd30-e8af-4fe3-a0d0-7ba8022bcba1" xlink:to="loc_us-gaap_CommonClassBMember_2a1392f7-5a81-4b23-a89c-532d0faae72e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_1ffc707d-bd8e-4e9f-9593-13a484db93c1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_04cd1e32-cf55-4d3a-a5f8-43200b19b838" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_1ffc707d-bd8e-4e9f-9593-13a484db93c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_1ffc707d-bd8e-4e9f-9593-13a484db93c1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1ffc707d-bd8e-4e9f-9593-13a484db93c1" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_1ffc707d-bd8e-4e9f-9593-13a484db93c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_09e1b250-bba2-4438-983e-eb74de466141" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1ffc707d-bd8e-4e9f-9593-13a484db93c1" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_09e1b250-bba2-4438-983e-eb74de466141" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_7d0b1eae-1d47-46ed-8f05-c7039ad6d2d6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_09e1b250-bba2-4438-983e-eb74de466141" xlink:to="loc_us-gaap_SubsequentEventMember_7d0b1eae-1d47-46ed-8f05-c7039ad6d2d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_a865e301-c7c3-47f6-b0a1-b4561a83fa7f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_b42de66b-016d-4c66-8630-06b1af0aefba" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_a865e301-c7c3-47f6-b0a1-b4561a83fa7f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_DividendsRate_591271d8-dbf0-4871-a726-a485caaf68c4" xlink:href="pwp-20240630.xsd#pwp_DividendsRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_b42de66b-016d-4c66-8630-06b1af0aefba" xlink:to="loc_pwp_DividendsRate_591271d8-dbf0-4871-a726-a485caaf68c4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#AwardTypeOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_TransactionPoolPsusMember_509e3332-24dc-44ef-a9a9-84d4c6cff9ff" xlink:href="pwp-20240630.xsd#pwp_TransactionPoolPsusMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_pwp_TransactionPoolPsusMember_509e3332-24dc-44ef-a9a9-84d4c6cff9ff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_GeneralRsusMember_2bc43628-98c7-492e-aaeb-69f9f2908098" xlink:href="pwp-20240630.xsd#pwp_GeneralRsusMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_pwp_GeneralRsusMember_2bc43628-98c7-492e-aaeb-69f9f2908098" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_GeneralAwardsMember_aa45815c-7f49-43da-9b7d-0f12f5a71996" xlink:href="pwp-20240630.xsd#pwp_GeneralAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_pwp_GeneralAwardsMember_aa45815c-7f49-43da-9b7d-0f12f5a71996" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_GeneralPSUsMember_7639f9ad-27bf-4902-9878-e20bb7a02cfd" xlink:href="pwp-20240630.xsd#pwp_GeneralPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_pwp_GeneralPSUsMember_7639f9ad-27bf-4902-9878-e20bb7a02cfd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ProfessionalPartnersAwardMember_f246107f-5db4-4865-87a5-abcc75be2d19" xlink:href="pwp-20240630.xsd#pwp_ProfessionalPartnersAwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_pwp_ProfessionalPartnersAwardMember_f246107f-5db4-4865-87a5-abcc75be2d19" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ProfessionalPartnersAwardsLiabilityClassifiedMember_8fc78047-6f5b-4182-8e80-b05263dca58e" xlink:href="pwp-20240630.xsd#pwp_ProfessionalPartnersAwardsLiabilityClassifiedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_pwp_ProfessionalPartnersAwardsLiabilityClassifiedMember_8fc78047-6f5b-4182-8e80-b05263dca58e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_AlignmentCapitalUnitsLiabilityClassifiedMember_d3d782c7-dbfe-4786-8731-9ccfa21b7ac4" xlink:href="pwp-20240630.xsd#pwp_AlignmentCapitalUnitsLiabilityClassifiedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_pwp_AlignmentCapitalUnitsLiabilityClassifiedMember_d3d782c7-dbfe-4786-8731-9ccfa21b7ac4" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_IncentivePlanAwardsMember_db29112f-67dd-47a3-ac5d-a99d1d783677" xlink:href="pwp-20240630.xsd#pwp_IncentivePlanAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_pwp_IncentivePlanAwardsMember_db29112f-67dd-47a3-ac5d-a99d1d783677" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_LegacyAwardsMember_591cd5ba-6067-4c39-8100-60f8a4b810cd" xlink:href="pwp-20240630.xsd#pwp_LegacyAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_pwp_LegacyAwardsMember_591cd5ba-6067-4c39-8100-60f8a4b810cd" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_pwp_ProfessionalPartnersAwardEquityClassifiedMember_709ecce6-2c8d-4e50-889a-b3386aabf023" xlink:href="pwp-20240630.xsd#pwp_ProfessionalPartnersAwardEquityClassifiedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_pwp_ProfessionalPartnersAwardEquityClassifiedMember_709ecce6-2c8d-4e50-889a-b3386aabf023" xlink:type="arc" order="12"/>
  </link:definitionLink>
</link:linkbase>
