<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
  <headerData>
    <submissionType>144</submissionType>
    <filerInfo>
      <filer>
        <filerCredentials>
          <cik>0001342075</cik>
          <ccc>XXXXXXXX</ccc>
        </filerCredentials>
      </filer>
      <liveTestFlag>LIVE</liveTestFlag>


    </filerInfo>
  </headerData>
  <formData>
    <issuerInfo>
      <issuerCik>0000354190</issuerCik>
      <issuerName>Arthur J. Gallagher &amp; Co.</issuerName>
      <secFileNumber>001-09761</secFileNumber>
      <issuerAddress>
        <com:street1>2850 GOLF ROAD</com:street1>
        <com:city>ROLLING MEADOWS</com:city>
        <com:stateOrCountry>IL</com:stateOrCountry>
        <com:zipCode>60008-4050</com:zipCode>
      </issuerAddress>
      <issuerContactPhone>630-773-3800</issuerContactPhone>
      <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>McCurdy Kay W</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
      <relationshipsToIssuer>
        <relationshipToIssuer>Former BOD</relationshipToIssuer>
      </relationshipsToIssuer>
    </issuerInfo>
    <securitiesInformation>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <brokerOrMarketmakerDetails>
        <name>Fidelity Brokerage Services LLC</name>
        <address>
          <com:street1>900 Salem Street</com:street1>
          <com:city>Smithfield</com:city>
          <com:stateOrCountry>RI</com:stateOrCountry>
          <com:zipCode>02917</com:zipCode>
        </address>
      </brokerOrMarketmakerDetails>
      <noOfUnitsSold>1200</noOfUnitsSold>
      <aggregateMarketValue>269070.00</aggregateMarketValue>
      <noOfUnitsOutstanding>215506000</noOfUnitsOutstanding>
      <approxSaleDate>08/04/2023</approxSaleDate>
      <securitiesExchangeName>NYSE</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>06/01/2016</acquiredDate>
      <natureOfAcquisitionTransaction>Restricted Stock Vesting</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>720</amountOfSecuritiesAcquired>
      <paymentDate>06/01/2016</paymentDate>
      <natureOfPayment>Compensation</natureOfPayment>
    </securitiesToBeSold>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>05/15/2019</acquiredDate>
      <natureOfAcquisitionTransaction>Restricted Stock Vesting</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>230</amountOfSecuritiesAcquired>
      <paymentDate>05/15/2019</paymentDate>
      <natureOfPayment>Compensation</natureOfPayment>
    </securitiesToBeSold>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>05/11/2022</acquiredDate>
      <natureOfAcquisitionTransaction>Restricted Stock Vesting</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>250</amountOfSecuritiesAcquired>
      <paymentDate>05/11/2022</paymentDate>
      <natureOfPayment>Compensation</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Kay W Mccurdy Rev Trust</name>
        <address>
          <com:street1>2850 Golf Road</com:street1>
          <com:city>Rolling Meadows</com:city>
          <com:stateOrCountry>IL</com:stateOrCountry>
          <com:zipCode>60008</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>05/09/2023</saleDate>
      <amountOfSecuritiesSold>1500</amountOfSecuritiesSold>
      <grossProceeds>324230.70</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Kay W Mccurdy Rev Trust</name>
        <address>
          <com:street1>2850 Golf Road</com:street1>
          <com:city>Rolling Meadows</com:city>
          <com:stateOrCountry>IL</com:stateOrCountry>
          <com:zipCode>60008</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>06/30/2023</saleDate>
      <amountOfSecuritiesSold>900</amountOfSecuritiesSold>
      <grossProceeds>197073.00</grossProceeds>
    </securitiesSoldInPast3Months>
    <remarks>This trade occurred in the Kay W Mccurdy Rev Trust account of which Kay McCurdy is a trustee.</remarks>
    <noticeSignature>
      <noticeDate>08/04/2023</noticeDate>
      <signature>/s/ Daniel Tucci, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Kay McCurdy</signature>
    </noticeSignature>
  </formData>
</edgarSubmission>
[{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 5223}]
144
0001342075
XXXXXXXX
LIVE
0000354190
Arthur J. Gallagher & Co.
001-09761
2850 GOLF ROAD
ROLLING MEADOWS
IL
60008-4050
630-773-3800
McCurdy Kay W
Former BOD
Common
Fidelity Brokerage Services LLC
900 Salem Street
Smithfield
RI
02917
1200
269070.00
215506000
08/04/2023
NYSE
Common
06/01/2016
Restricted Stock Vesting
Issuer
N
720
06/01/2016
Compensation
Common
05/15/2019
Restricted Stock Vesting
Issuer
N
230
05/15/2019
Compensation
Common
05/11/2022
Restricted Stock Vesting
Issuer
N
250
05/11/2022
Compensation
N
Kay W Mccurdy Rev Trust
2850 Golf Road
Rolling Meadows
IL
60008
Common
05/09/2023
1500
324230.70
Kay W Mccurdy Rev Trust
2850 Golf Road
Rolling Meadows
IL
60008
Common
06/30/2023
900
197073.00
This trade occurred in the Kay W Mccurdy Rev Trust account of which Kay McCurdy is a trustee.
08/04/2023
/s/ Daniel Tucci, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Kay McCurdy