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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:e33185ad-3e15-42ab-9cbb-0471061c368d,g:39d577e4-7dfa-417a-aec1-d731df3cb2e5-->
<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://www.firstmerchants.com/role/DocumentandEntityInformationDocument" xlink:type="simple" xlink:href="frme-20240826.xsd#DocumentandEntityInformationDocument"/>
  <link:definitionLink xlink:role="http://www.firstmerchants.com/role/DocumentandEntityInformationDocument" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityListingsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsTable_4d2e5d79-ec73-4376-a3bf-561e176fa123" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityListingsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityListingsTable_4d2e5d79-ec73-4376-a3bf-561e176fa123" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_3e53d7aa-4303-46df-8a95-61cabff5407a" 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_EntityListingsTable_4d2e5d79-ec73-4376-a3bf-561e176fa123" xlink:to="loc_us-gaap_StatementClassOfStockAxis_3e53d7aa-4303-46df-8a95-61cabff5407a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_3e53d7aa-4303-46df-8a95-61cabff5407a_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_3e53d7aa-4303-46df-8a95-61cabff5407a" xlink:to="loc_us-gaap_ClassOfStockDomain_3e53d7aa-4303-46df-8a95-61cabff5407a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_6e0be7b8-b8dd-47e0-a8df-3348b0e51d03" 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_3e53d7aa-4303-46df-8a95-61cabff5407a" xlink:to="loc_us-gaap_ClassOfStockDomain_6e0be7b8-b8dd-47e0-a8df-3348b0e51d03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_c49e50b8-5b5d-45a7-b77b-bc41fd246280" 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_ClassOfStockDomain_6e0be7b8-b8dd-47e0-a8df-3348b0e51d03" xlink:to="loc_us-gaap_CommonStockMember_c49e50b8-5b5d-45a7-b77b-bc41fd246280" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_frme_DepositarySharesMember_826263f7-89f2-47b6-9486-5c7120bab854" xlink:href="frme-20240826.xsd#frme_DepositarySharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_6e0be7b8-b8dd-47e0-a8df-3348b0e51d03" xlink:to="loc_frme_DepositarySharesMember_826263f7-89f2-47b6-9486-5c7120bab854" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_23a5aacc-6aa9-43b7-88dc-88429789128b" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_DocumentType_23a5aacc-6aa9-43b7-88dc-88429789128b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_d1cb7f9e-f82f-4a55-a623-cb6c4579c472" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_DocumentPeriodEndDate_d1cb7f9e-f82f-4a55-a623-cb6c4579c472" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_3078ae75-2b11-42af-9937-9c200017ae9a" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityRegistrantName_3078ae75-2b11-42af-9937-9c200017ae9a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_85901342-8d51-4168-9c40-74e2e715955d" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityIncorporationStateCountryCode_85901342-8d51-4168-9c40-74e2e715955d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_9fbbb24b-65d6-4de6-9017-395cd412c230" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityFileNumber_9fbbb24b-65d6-4de6-9017-395cd412c230" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_031ef82b-7348-4f6f-9824-1fafdfada6b4" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityTaxIdentificationNumber_031ef82b-7348-4f6f-9824-1fafdfada6b4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_72ba1dab-ad9d-42c2-bbf8-c9ec482f4cea" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityAddressAddressLine1_72ba1dab-ad9d-42c2-bbf8-c9ec482f4cea" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_ab44b779-6a15-4f5a-a2f8-7b04b022f748" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityAddressAddressLine2_ab44b779-6a15-4f5a-a2f8-7b04b022f748" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_29c61344-a23f-4ee8-90b0-28251240ea02" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityAddressCityOrTown_29c61344-a23f-4ee8-90b0-28251240ea02" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_21d0d09c-d41c-426b-878f-b679d204bafa" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityAddressStateOrProvince_21d0d09c-d41c-426b-878f-b679d204bafa" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_fb217ec7-72c1-4ea9-9a5f-01ccd2a0d522" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityAddressPostalZipCode_fb217ec7-72c1-4ea9-9a5f-01ccd2a0d522" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_fd746863-3c85-4eac-84a3-ffd7eb2b725b" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_CityAreaCode_fd746863-3c85-4eac-84a3-ffd7eb2b725b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_533a8f3f-4d56-4a5d-a18e-bcfc3644fade" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_LocalPhoneNumber_533a8f3f-4d56-4a5d-a18e-bcfc3644fade" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_47625569-8e20-4002-8c4e-d9103715e3ea" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_Security12bTitle_47625569-8e20-4002-8c4e-d9103715e3ea" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_82952d35-2f4f-4835-bc27-d52096bb3c2d" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_TradingSymbol_82952d35-2f4f-4835-bc27-d52096bb3c2d" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_877ce142-5023-4ed1-a63b-2f7022e4e5d9" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_SecurityExchangeName_877ce142-5023-4ed1-a63b-2f7022e4e5d9" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_45cb9cbb-baf2-45f7-8e2d-97cb84224096" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_WrittenCommunications_45cb9cbb-baf2-45f7-8e2d-97cb84224096" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_b8276527-14a8-4657-aec0-d39dd86e9c1e" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_SolicitingMaterial_b8276527-14a8-4657-aec0-d39dd86e9c1e" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_02e95549-7d36-4dac-b22c-8f39747058dd" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_PreCommencementTenderOffer_02e95549-7d36-4dac-b22c-8f39747058dd" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_753df9ad-0adc-4f3e-bf43-0f6073262067" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_753df9ad-0adc-4f3e-bf43-0f6073262067" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_fa39a1c9-aeff-45f3-8e15-aecfb0a0c220" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityEmergingGrowthCompany_fa39a1c9-aeff-45f3-8e15-aecfb0a0c220" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_4b15aeeb-742e-48de-8737-d65042bc8244" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_EntityCentralIndexKey_4b15aeeb-742e-48de-8737-d65042bc8244" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_25aaa431-0231-4278-8232-9bc0b189c49e" 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_EntityListingsLineItems_0eba7524-2b94-4c5c-989b-203daa02f728" xlink:to="loc_dei_AmendmentFlag_25aaa431-0231-4278-8232-9bc0b189c49e" xlink:type="arc" order="22"/>
  </link:definitionLink>
</link:linkbase>
