尼索思美股招股说明书(2026-05-12版)

$1,250,000,000 $500,000,000 4.750% Notes due 2031$750,000,000 5.300% Notes due 2036 We are offering $1,250,000,000 aggregate principal amount of notes in two series. We are offering $500,000,000 aggregate principal amount of our notes due2031 (the “2031 Notes”) and $750,000,000 aggregate principal amount of our notes due 2036 (the “2036 Notes” and, together with the 2031 Notes, the “Notes”). The2031 Notes will bear interest at a rate of 4.750% per year. Interest on the 2031 Notes will be paid semi-annually in arrears on May 18 and November 18 of each year,beginning November 18, 2026. The 2036 Notes will bear interest at a rate of 5.300% per year. Interest on the 2036 Notes will be paid semi-annually in arrears on May 18and November 18 of each year, beginning November 18, 2026. The 2031 Notes will mature on May 18, 2031. The 2036 Notes will mature on May 18, 2036. At our option, we may redeem some or all of the Notes of either series at any time and from time to time at the applicable redemption price described herein. If a Tax Credit Event (as defined below) occurs, we may redeem, at our option, each series of the Notes, in whole but not in part, at a redemption price equal to101% of the principal amount of the Notes being redeemed, plus accrued and unpaid interest to but excluding the redemption date. See the “Supplemental Description ofthe Notes —Tax Credit Event Redemption” section of this prospectus supplement for more information. Each series of the Notes will be issued in denominations of $2,000 and integral multiples of $1,000 in excess thereof. Investing in the Notes involves risks. For a discussion of these risks, please refer to “Risk Factors” beginning on pageS-7 ofthis prospectus supplement and the “Risk Factors” section in our most recent Annual Report on Form 10-K. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the Notes or passed upon theadequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense. This prospectus supplement and the accompanying prospectus are not intended to constitute an offer to, and the Notes should not be purchased, held orotherwise acquired by, a “specified foreign entity” as defined in Section7701(a)(51)(B) of the Internal Revenue Code of 1986, as amended (an “SFE”). Bypurchasing Notes, any investor in the Notes (including all affiliated entities that participate in such purchase) will be deemed to represent and warrant to usthat it is not, and will not be, for its taxable year that includes the date of the original issuance of the Notes, an SFE. (1)Plus accrued interest from May 18, 2026, if settlement occurs after that date. Each series of Notes will constitute a new issuance of securities with no established trading market. The Notes will not be listed on any securities exchange nor dowe intend to seek their quotation on any automated dealer quotation system. We expect that delivery of the Notes will be made to investors through the book-entry delivery system of The Depository Trust Company (“DTC”) for theaccounts of its participants, including Clearstream Banking S.A. (“Clearstream”) and Euroclear Bank SA/NV (“Euroclear”), on or about May 18, 2026. US BancorpScotiabank BNP PARIBASHuntington CapitalMarkets AcademySecurities Table of Contents TABLE OF CONTENTSProspectus Supplement ABOUT THIS PROSPECTUS SUPPLEMENTFORWARD-LOOKING STATEMENTSWHERE YOU CAN FIND MORE INFORMATIONINCORPORATION BY REFERENCESUMMARYTHE OFFERINGRISK FACTORSUSE OF PROCEEDSSUPPLEMENTAL DESCRIPTION OF THE NOTESCERTAIN UNITED STATES FEDERAL INCOME TAX CONSIDERATIONSUNDERWRITING (CONFLICTS OF INTEREST)LEGAL MATTERSEXPERTS Prospectus ABOUT THIS PROSPECTUSNISOURCE INC.RISK FACTORSFORWARD-LOOKING STATEMENTSWHERE YOU CAN FIND MORE INFORMATIONINCORPORATION BY REFERENCEUSE OF PROCEEDSDESCRIPTION OF CAPITAL STOCKDESCRIPTION OF DEPOSITARY SHARESDESCRIPTION OF THE DEBT SECURITIESDESCRIPTION OF WARRANTSDESCRIPTION OF STOCK PURCHASE CONTRACTS AND STOCK PURCHASE UNITSBOOK-ENTRY ISSUANCEPLAN OF DISTRIBUTIONLEGAL MATTERSEXPERTS Table of Contents ABOUT THIS PROSPECTUS SUPPLEMENT This document is in two parts. The first part, this prospectus supplement, describes the specific terms of this offering of the Notes and certain othermatters relating to NiSource Inc. The second part, the accompanying prospectus, gives more general information, some of which does not apply to thisoffering. To the extent there is a conflict or inconsistency between the information contained or incorporated by reference in this prospectus supplement(or any related free writing prospectus issued by us), on the one hand, and the information contained or incorporated by reference in the accompanyingprospectus, the information contained or incorporated by reference in this prospectus supplement (or any related free writing prospectus issued by us)shall control. The registration