<?xml version="1.0" encoding="UTF-8"?><ns2:edgarSubmission xmlns:com="http://www.sec.gov/edgar/common" xmlns:ns2="http://www.sec.gov/edgar/ownership">
    <ns2:headerData>
        <ns2:submissionType>144</ns2:submissionType>
        <ns2:filerInfo>
            <ns2:filer>
                <ns2:filerCredentials>
                    <ns2:cik>0001909078</ns2:cik>
                    <ns2:ccc>XXXXXXXX</ns2:ccc>
                </ns2:filerCredentials>
            </ns2:filer>
            <ns2:liveTestFlag>LIVE</ns2:liveTestFlag>



        </ns2:filerInfo>
    </ns2:headerData>
    <ns2:formData>
        <ns2:issuerInfo>
            <ns2:issuerCik>0000860413</ns2:issuerCik>
            <ns2:issuerName>First Interstate BancSystem, Inc.</ns2:issuerName>
            <ns2:secFileNumber>001-34653</ns2:secFileNumber>
            <ns2:issuerAddress>
                <com:street1>401 North 31st Street</com:street1>
                <com:city>Billings</com:city>
                <com:stateOrCountry>MT</com:stateOrCountry>
                <com:zipCode>59101</com:zipCode>
            </ns2:issuerAddress>
            <ns2:issuerContactPhone>1-406-255-5311</ns2:issuerContactPhone>
            <ns2:nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Juliana Sarah Scott Rose Trust dtd 11/02/2006</ns2:nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <ns2:relationshipsToIssuer>
                <ns2:relationshipToIssuer>Member of immediate family of any of the foregoing</ns2:relationshipToIssuer>
            </ns2:relationshipsToIssuer>
        </ns2:issuerInfo>
        <ns2:securitiesInformation>
            <ns2:securitiesClassTitle>Common</ns2:securitiesClassTitle>
            <ns2:brokerOrMarketmakerDetails>
                <ns2:name>Goldman Sachs &amp; Co. LLC</ns2:name>
                <ns2:address>
                    <com:street1>200 West Street</com:street1>
                    <com:city>New York</com:city>
                    <com:stateOrCountry>NY</com:stateOrCountry>
                    <com:zipCode>10282</com:zipCode>
                </ns2:address>
            </ns2:brokerOrMarketmakerDetails>
            <ns2:noOfUnitsSold>47532</ns2:noOfUnitsSold>
            <ns2:aggregateMarketValue>1213016.64</ns2:aggregateMarketValue>
            <ns2:noOfUnitsOutstanding>104568019</ns2:noOfUnitsOutstanding>
            <ns2:approxSaleDate>06/11/2024</ns2:approxSaleDate>
            <ns2:securitiesExchangeName>NASD</ns2:securitiesExchangeName>
        </ns2:securitiesInformation>
        <ns2:securitiesToBeSold>
            <ns2:securitiesClassTitle>Common</ns2:securitiesClassTitle>
            <ns2:acquiredDate>06/20/2020</ns2:acquiredDate>
            <ns2:natureOfAcquisitionTransaction>Acquired as an inheritance from an estate</ns2:natureOfAcquisitionTransaction>
            <ns2:nameOfPersonfromWhomAcquired>Scott Family Member</ns2:nameOfPersonfromWhomAcquired>
            <ns2:isGiftTransaction>N</ns2:isGiftTransaction>
            <ns2:amountOfSecuritiesAcquired>11983</ns2:amountOfSecuritiesAcquired>
            <ns2:paymentDate>06/20/2020</ns2:paymentDate>
            <ns2:natureOfPayment>None</ns2:natureOfPayment>
        </ns2:securitiesToBeSold>
        <ns2:securitiesToBeSold>
            <ns2:securitiesClassTitle>Common</ns2:securitiesClassTitle>
            <ns2:acquiredDate>11/15/2022</ns2:acquiredDate>
            <ns2:natureOfAcquisitionTransaction>Acquired as an inheritance from an estate</ns2:natureOfAcquisitionTransaction>
            <ns2:nameOfPersonfromWhomAcquired>Scott Family Member</ns2:nameOfPersonfromWhomAcquired>
            <ns2:isGiftTransaction>N</ns2:isGiftTransaction>
            <ns2:amountOfSecuritiesAcquired>25901</ns2:amountOfSecuritiesAcquired>
            <ns2:paymentDate>11/15/2022</ns2:paymentDate>
            <ns2:natureOfPayment>None</ns2:natureOfPayment>
        </ns2:securitiesToBeSold>
        <ns2:securitiesToBeSold>
            <ns2:securitiesClassTitle>Common</ns2:securitiesClassTitle>
            <ns2:acquiredDate>12/16/1971</ns2:acquiredDate>
            <ns2:natureOfAcquisitionTransaction>Acquired as an inheritance from an estate</ns2:natureOfAcquisitionTransaction>
            <ns2:nameOfPersonfromWhomAcquired>Scott Family Member</ns2:nameOfPersonfromWhomAcquired>
            <ns2:isGiftTransaction>N</ns2:isGiftTransaction>
            <ns2:amountOfSecuritiesAcquired>9648</ns2:amountOfSecuritiesAcquired>
            <ns2:paymentDate>12/16/1971</ns2:paymentDate>
            <ns2:natureOfPayment>None</ns2:natureOfPayment>
        </ns2:securitiesToBeSold>
        <ns2:nothingToReportFlagOnSecuritiesSoldInPast3Months>N</ns2:nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <ns2:securitiesSoldInPast3Months>
            <ns2:sellerDetails>
                <ns2:name>Juliana Sarah Scott Rose Trust dtd 11/02/2006</ns2:name>
                <ns2:address>
                    <com:street1>401 North 31st Street</com:street1>
                    <com:city>Billings</com:city>
                    <com:stateOrCountry>MT</com:stateOrCountry>
                    <com:zipCode>59101</com:zipCode>
                </ns2:address>
            </ns2:sellerDetails>
            <ns2:securitiesClassTitle>Common</ns2:securitiesClassTitle>
            <ns2:saleDate>05/14/2024</ns2:saleDate>
            <ns2:amountOfSecuritiesSold>27000</ns2:amountOfSecuritiesSold>
            <ns2:grossProceeds>742413.04</ns2:grossProceeds>
        </ns2:securitiesSoldInPast3Months>
        <ns2:noticeSignature>
            <ns2:noticeDate>06/11/2024</ns2:noticeDate>
            <ns2:planAdoptionDates/>
            <ns2:signature>Goldman Sachs &amp; Co. LLC on behalf of Juliana Sarah Scott Rose Trust dtd 11/02/2006</ns2:signature>
        </ns2:noticeSignature>
    </ns2:formData>
</ns2:edgarSubmission>
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144
0001909078
XXXXXXXX
LIVE
0000860413
First Interstate BancSystem, Inc.
001-34653
401 North 31st Street
Billings
MT
59101
1-406-255-5311
Juliana Sarah Scott Rose Trust dtd 11/02/2006
Member of immediate family of any of the foregoing
Common
Goldman Sachs & Co. LLC
200 West Street
New York
NY
10282
47532
1213016.64
104568019
06/11/2024
NASD
Common
06/20/2020
Acquired as an inheritance from an estate
Scott Family Member
N
11983
06/20/2020
None
Common
11/15/2022
Acquired as an inheritance from an estate
Scott Family Member
N
25901
11/15/2022
None
Common
12/16/1971
Acquired as an inheritance from an estate
Scott Family Member
N
9648
12/16/1971
None
N
Juliana Sarah Scott Rose Trust dtd 11/02/2006
401 North 31st Street
Billings
MT
59101
Common
05/14/2024
27000
742413.04
06/11/2024
Goldman Sachs & Co. LLC on behalf of Juliana Sarah Scott Rose Trust dtd 11/02/2006