<SEC-DOCUMENT>0001127602-25-007960.txt : 20250304
<SEC-HEADER>0001127602-25-007960.hdr.sgml : 20250304
<ACCEPTANCE-DATETIME>20250304170808
ACCESSION NUMBER:		0001127602-25-007960
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250228
FILED AS OF DATE:		20250304
DATE AS OF CHANGE:		20250304

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Yates Lloyd M
		CENTRAL INDEX KEY:			0001311411
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-16189
		FILM NUMBER:		25706119

	MAIL ADDRESS:	
		STREET 1:		1N 2ND ST
		CITY:			HARTSVILLE
		STATE:			SC
		ZIP:			29550

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>2025-02-28</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001311411</rptOwnerCik>
            <rptOwnerName>Yates Lloyd M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>801 E. 86TH AVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MERRILLVILLE</rptOwnerCity>
            <rptOwnerState>IN</rptOwnerState>
            <rptOwnerZipCode>46410</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <officerTitle>Director and President &amp; CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-02-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>233689</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>40.81</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>476608.6988</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-02-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>96164</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>40.81</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>380444.6988</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-02-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>12653</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>40.81</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>367791.6988</value>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Vesting of non-derivative performance stock units granted in 2022, which are exempt from liability under Section 16(b) of the Securities Exchange Act pursuant to rule 16b-3(d).</footnote>
        <footnote id="F2">Number of shares reported represent shares withheld to satisfy tax withholding obligations in connection with the vesting of the performance stock units above.</footnote>
        <footnote id="F3">Number of shares reported represent shares withheld to satisfy tax withholding obligations in connection with the vesting of the 2022 Restricted Stock Unit award.</footnote>
        <footnote id="F4">Includes shares acquired through the NiSource Inc. Employee Stock Purchase Plan.</footnote>
        <footnote id="F5">This amount includes RSUs received pursuant to the dividend equivalent provisions of his director RSU awards from 2020 and 2021, and which are subject to the same vesting conditions as the underlying RSUs.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Ashley Bancroft, Attorney-in-Fact</signatureName>
        <signatureDate>2025-03-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
