<SEC-DOCUMENT>0001127602-24-009009.txt : 20240307
<SEC-HEADER>0001127602-24-009009.hdr.sgml : 20240307
<ACCEPTANCE-DATETIME>20240307161616
ACCESSION NUMBER:		0001127602-24-009009
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20240306
FILED AS OF DATE:		20240307
DATE AS OF CHANGE:		20240307

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Brown Donald Eugene
		CENTRAL INDEX KEY:			0001638426
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-16189
		FILM NUMBER:		24730330

	MAIL ADDRESS:	
		STREET 1:		801 E. 86TH AVENUE
		CITY:			MERRILLVILLE
		STATE:			IN
		ZIP:			46410

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NISOURCE INC.
		CENTRAL INDEX KEY:			0001111711
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRIC & OTHER SERVICES COMBINED [4931]
		ORGANIZATION NAME:           	01 Energy & Transportation
		IRS NUMBER:				352108964
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		801 EAST 86TH AVE
		CITY:			MERRILLVILLE
		STATE:			IN
		ZIP:			46410-6272
		BUSINESS PHONE:		2196475200

	MAIL ADDRESS:	
		STREET 1:		801 EAST 86TH AVE
		CITY:			MERRILLVILLE
		STATE:			IN
		ZIP:			46410-6272

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	NISOURCE INC/DE
		DATE OF NAME CHANGE:	20001103

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	NEW NISOURCE INC
		DATE OF NAME CHANGE:	20000412
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-03-06</periodOfReport>

    <issuer>
        <issuerCik>0001111711</issuerCik>
        <issuerName>NISOURCE INC.</issuerName>
        <issuerTradingSymbol>NI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001638426</rptOwnerCik>
            <rptOwnerName>Brown Donald Eugene</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>NISOURCE INC.</rptOwnerStreet1>
            <rptOwnerStreet2>801 E. 86TH AVENUE</rptOwnerStreet2>
            <rptOwnerCity>MERRILLVILLE</rptOwnerCity>
            <rptOwnerState>IN</rptOwnerState>
            <rptOwnerZipCode>46410</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>EVP &amp; Chief Innovation Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-03-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>37490</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>26.78</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>195855</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2471.1488</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>401(k)</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $26.770 to $26.795, inclusive. The reporting person undertakes to provide to NiSource Inc., any security holder of NiSource Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.</footnote>
        <footnote id="F2">Constitutes shares acquired through the NiSource Inc. Retirement Savings Plan through March 6, 2024.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Kimberly S. Cuccia, Attorney-in-Fact</signatureName>
        <signatureDate>2024-03-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
