<SEC-DOCUMENT>0001950047-25-000900.txt : 20250214
<SEC-HEADER>0001950047-25-000900.hdr.sgml : 20250214
<ACCEPTANCE-DATETIME>20250214164755
ACCESSION NUMBER:		0001950047-25-000900
CONFORMED SUBMISSION TYPE:	144
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20250214
DATE AS OF CHANGE:		20250214

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FIRST INTERSTATE BANCSYSTEM INC
		CENTRAL INDEX KEY:			0000860413
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		ORGANIZATION NAME:           	02 Finance
		IRS NUMBER:				810331430
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		144
		SEC ACT:		1933 Act
		SEC FILE NUMBER:	001-34653
		FILM NUMBER:		25630230

	BUSINESS ADDRESS:	
		STREET 1:		401 NO 31ST STREET
		CITY:			BILLINGS
		STATE:			MT
		ZIP:			59101
		BUSINESS PHONE:		4062555311

	MAIL ADDRESS:	
		STREET 1:		401 NO 31ST STREET
		CITY:			BILLINGS
		STATE:			MT
		ZIP:			59101

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	FIRST INTERSTATE BANCSYSTEM OF MONTANA INC
		DATE OF NAME CHANGE:	19930615

REPORTING-OWNER:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			HEYNEMAN JOHN M JR
		CENTRAL INDEX KEY:			0001198518
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		144

	MAIL ADDRESS:	
		STREET 1:		C/O FIRST INTERSTATE BANCSYSTEM INC
		STREET 2:		P O BOX 30918
		CITY:			BILLINGS
		STATE:			MT
		ZIP:			59116
</SEC-HEADER>
<DOCUMENT>
<TYPE>144
<SEQUENCE>1
<FILENAME>primary_doc.xml
<TEXT>
<XML>
<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:ns2="http://www.sec.gov/edgar/common">
    <headerData>
        <submissionType>144</submissionType>
        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001198518</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0000860413</issuerCik>
            <issuerName>FIRST INTERSTATE BANCSYSTEM INC.</issuerName>
            <secFileNumber>001-34653</secFileNumber>
            <issuerAddress>
                <ns2:street1>401 North 31st Street</ns2:street1>
                <ns2:city>Billings</ns2:city>
                <ns2:stateOrCountry>MT</ns2:stateOrCountry>
                <ns2:zipCode>59101</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>(406) 255-5311</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>BAE-JOHN HEYNEMAN</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Director's son</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>1335</noOfUnitsSold>
            <aggregateMarketValue>43461.33</aggregateMarketValue>
            <noOfUnitsOutstanding>104529863</noOfUnitsOutstanding>
            <approxSaleDate>02/14/2025</approxSaleDate>
            <securitiesExchangeName>NASDAQ</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>01/02/1976</acquiredDate>
            <natureOfAcquisitionTransaction>Gift from Affiliate</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>John Heyneman Jr</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>Y</isGiftTransaction>
            <donarAcquiredDate>06/27/2018</donarAcquiredDate>
            <amountOfSecuritiesAcquired>1335</amountOfSecuritiesAcquired>
            <natureOfPayment>NA</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <noticeSignature>
            <noticeDate>02/14/2025</noticeDate>
            <planAdoptionDates/>
            <signature>/s/ John M Heyneman Jr</signature>
        </noticeSignature>
    </formData>
</edgarSubmission>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
