<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:ns2="http://www.sec.gov/edgar/common">
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        <submissionType>144</submissionType>
        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001416752</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0001408198</issuerCik>
            <issuerName>MSCI INC.</issuerName>
            <secFileNumber>001-33812</secFileNumber>
            <issuerAddress>
                <ns2:street1>7 World Trade Center,</ns2:street1>
                <ns2:street2>250 Greenwich Street, 49th Floor</ns2:street2>
                <ns2:city>New York</ns2:city>
                <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                <ns2:zipCode>10007</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>212-804-3900</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>CARROLL DOUGLAS BAER PETTIT</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Officer</relationshipToIssuer>
                <relationshipToIssuer>Director</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC Executive Financial Services</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>8th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>5000</noOfUnitsSold>
            <aggregateMarketValue>2762970.00</aggregateMarketValue>
            <noOfUnitsOutstanding>77371495</noOfUnitsOutstanding>
            <approxSaleDate>05/05/2025</approxSaleDate>
            <securitiesExchangeName>NYSE</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>02/07/2022</acquiredDate>
            <natureOfAcquisitionTransaction>Performance Shares</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>4941</amountOfSecuritiesAcquired>
            <paymentDate>02/07/2022</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>02/08/2023</acquiredDate>
            <natureOfAcquisitionTransaction>Performance Shares</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>59</amountOfSecuritiesAcquired>
            <paymentDate>02/08/2023</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>CARROLL DOUGLAS BAER PETTIT</name>
                <address>
                    <ns2:street1>7 World Trade Center,</ns2:street1>
                    <ns2:street2>250 Greenwich Street, 49th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10007</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>04/04/2025</saleDate>
            <amountOfSecuritiesSold>5000</amountOfSecuritiesSold>
            <grossProceeds>2621240.50</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>CARROLL DOUGLAS BAER PETTIT</name>
                <address>
                    <ns2:street1>7 World Trade Center,</ns2:street1>
                    <ns2:street2>250 Greenwich Street, 49th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10007</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>03/05/2025</saleDate>
            <amountOfSecuritiesSold>5000</amountOfSecuritiesSold>
            <grossProceeds>2841800.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <noticeSignature>
            <noticeDate>05/05/2025</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>12/04/2024</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ C. D. Baer Pettit</signature>
        </noticeSignature>
    </formData>
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144
0001416752
XXXXXXXX
LIVE
0001408198
MSCI INC.
001-33812
7 World Trade Center,
250 Greenwich Street, 49th Floor
New York
NY
10007
212-804-3900
CARROLL DOUGLAS BAER PETTIT
Officer
Director
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
5000
2762970.00
77371495
05/05/2025
NYSE
Common
02/07/2022
Performance Shares
ISSUER
N
4941
02/07/2022
Not Applicable
Common
02/08/2023
Performance Shares
ISSUER
N
59
02/08/2023
Not Applicable
N
CARROLL DOUGLAS BAER PETTIT
7 World Trade Center,
250 Greenwich Street, 49th Floor
New York
NY
10007
Common
04/04/2025
5000
2621240.50
CARROLL DOUGLAS BAER PETTIT
7 World Trade Center,
250 Greenwich Street, 49th Floor
New York
NY
10007
Common
03/05/2025
5000
2841800.00
05/05/2025
12/04/2024
/s/ C. D. Baer Pettit