NI / NiSource Inc. - SEC-Einreichungen, Jahresbericht, Proxy Statement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 18, 2026 NiSource Inc. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 18, 2026 NiSource Inc. (Exact Name of Registrant as Specified in Charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.R.S. E

5.300% Notes due 2036

EX-4.2 Exhibit 4.2 UNLESS THIS GLOBAL NOTE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), NEW YORK, NEW YORK, TO NISOURCE INC. OR ITS AGENT OR AGENTS FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY GLOBAL NOTE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF

4.750% Notes due 2031

EX-4.1 Exhibit 4.1 UNLESS THIS GLOBAL NOTE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), NEW YORK, NEW YORK, TO NISOURCE INC. OR ITS AGENT OR AGENTS FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY GLOBAL NOTE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 11, 2026 NiSource Inc. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 11, 2026 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.

Security Type

Calculation of Filing Fee Tables S-3 NISOURCE INC. Table 1: Newly Registered and Carry Forward Securities ☐Not Applicable Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry Forward Form Type Carry Forward File Number Carry Forward Initial Effec

$1,250,000,000 $500,000,000 4.750% Notes due 2031 $750,000,000 5.300% Notes due 2036

424B2 Table of Contents Filed Pursuant to Rule 424(b)(2) File No. 333-291167 Prospectus Supplement (To Prospectus dated October 30, 2025) $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 due 2031 (the “2031 Notes”

NiSource Inc. $500,000,000 4.750% Notes due 2031 $750,000,000 5.300% Notes due 2036 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated May 11, 2026 (the “Preliminary Prospectus Supplement”)) Issuer: NiSource Inc. Security: 4.750% Notes du

FWP Filed Pursuant to Rule 433 Registration Statement (No. 333-291167) May 11, 2026 NiSource Inc. $500,000,000 4.750% Notes due 2031 $750,000,000 5.300% Notes due 2036 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated May 11, 2026 (the “Preliminary Prospectus Supplement”)) Issuer: NiSource Inc. Security: 4.750% Notes due 2031 (the “ 2031 Notes”) 5.300% Notes due 2036 (the “2036 Notes”

Subject to Completion, dated May 11, 2026

424B5 Table of Contents Filed Pursuant to Rule 424(b)(5) File No. 333-291167 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted

NiSource announces first quarter results

Exhibit 99.1 FOR IMMEDIATE RELEASE May 6, 2026 FOR ADDITIONAL INFORMATION Media Investors [email protected] [email protected] NiSource announces first quarter results •GenCo cost savings expand to approximately $1.4 billion for existing customers through Alphabet and Amazon collaboration •Raising 2026-2033 non-GAAP consolidated adjusted EPS compound annual growth rate to 9%-10% •Reaffirming

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 6, 2026 NiSource Inc. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 6, 2026 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission file

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2026 ☐ TRANSITION REPORT PURSUANT TO

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2026 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   )

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   )         Filed by the Registrant ☒     Filed by a Party other than the Registrant ☐         Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commis

ARS

ANNUAL REPORT Driving Value through Transformation2 Message from our President DQG&KLHI([HFXWLYH2ႈFHU  Message from our Chair 6 Board of Directors and Senior Management Team 9 Stockholder Information එඖඛඑඌඍ ඊඉඋඓඋ඗ඞඍක Company Information ඊඉඋඓඋ඗ඞඍක What's Inside ,QZHGHOLYHUHGVWURQJ¿QDQFLDOSHUIRUPDQFHDQGDGYDQFHG VWUDWHJLFSULRULWLHVWKDWSRVLWLRQ1L6RXUFH for long-term growth.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 11, 2025 NiSource Inc. (

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 11, 2025 NiSource Inc. (Exact Name of Registrant as Specified in Charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.R

SEVENTH AMENDED AND RESTATED REVOLVING CREDIT AGREEMENT NISOURCE INC., as Borrower, THE LENDERS PARTY HERETO, BARCLAYS BANK PLC, as Administrative Agent, JPMORGAN CHASE BANK, N.A., MUFG BANK, LTD. and WELLS FARGO BANK, NATIONAL ASSOCIATION, as Co-Syn

EX-10.1 Exhibit 10.1 SEVENTH AMENDED AND RESTATED REVOLVING CREDIT AGREEMENT among NISOURCE INC., as Borrower, THE LENDERS PARTY HERETO, BARCLAYS BANK PLC, as Administrative Agent, JPMORGAN CHASE BANK, N.A., MUFG BANK, LTD. and WELLS FARGO BANK, NATIONAL ASSOCIATION, as Co-Syndication Agents, and BANK OF AMERICA, NATIONAL ASSOCIATION, BANK OF MONTREAL and MIZUHO BANK, LTD., as Co-Documentation Age

As filed with the Securities and Exchange Commission on November 7, 2025

S-8 As filed with the Securities and Exchange Commission on November 7, 2025 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 7, 2025 NiSource Inc. (E

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 7, 2025 NiSource Inc. (Exact Name of Registrant as Specified in Charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.R.

Table 1: Newly Registered Securities

Calculation of Filing Fee Tables S-8 NISOURCE INC. Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee 1 Equity Common Stock, par value $0.01 per share Other 1,500,000 $ 42.06 $ 63,090,000.00 0.0001381 $ 8,712.73 Total Offering Amo

NISOURCE INC. THE BANK OF NEW YORK MELLON Third Supplemental Indenture Dated as of November 7, 2025 5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056

EX-4.1 Exhibit 4.1 NISOURCE INC. TO THE BANK OF NEW YORK MELLON Trustee Third Supplemental Indenture Dated as of November 7, 2025 5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056 TABLE OF CONTENTS Page ARTICLE 1 DEFINITIONS 1 Section 1.1 Defined Terms 1 ARTICLE 2 DESIGNATION OF THE NOTES 4 Section 2.1 Designation and Principal Amount 4 Section 2.2 Form of the Notes 5 Section 2.3

FIRST AMENDMENT TO THE NISOURCE INC. RETIREMENT SAVINGS PLAN Background Information

EX-99.2 Exhibit 99.2 FIRST AMENDMENT TO THE NISOURCE INC. RETIREMENT SAVINGS PLAN Background Information A. NiSource Inc. (the “Company”) maintains the NiSource Inc. Retirement Savings Plan, amended and restated effective as of January 1, 2024 (the “Plan”). B. The NiSource Benefits Committee (the “Committee”) has the power to amend the Plan pursuant to Section 14.02 thereof. C. The Committee desir

NISOURCE INC. RETIREMENT SAVINGS PLAN Amended and Restated Effective as of January 1, 2024

EX-99.1 Exhibit 99.1 NISOURCE INC. RETIREMENT SAVINGS PLAN Amended and Restated Effective as of January 1, 2024 TABLE OF CONTENTS ARTICLE I DEFINITIONS 3 Section 1.01 AB I Benefit 3 Section 1.02 AB II Benefit 3 Section 1.03 Account (or Account Balance) 3 Section 1.04 After-tax Contribution Account 3 Section 1.05 Bay State 3 Section 1.06 Bay State Pension Plan 3 Section 1.07 Bay State Union 401(k)

$1,000,000,000 5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056

424B2 Table of Contents Filed pursuant to Rule 424(b)(2) File No. 333-291167 Prospectus Supplement (To Prospectus dated October 30, 2025) $1,000,000,000 5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056 We are offering $1,000,000,000 of our 5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056 (the “Notes”). The Notes will bear interest (i) from and including Novemb

NiSource Inc. $1,000,000,000 5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated November 3, 2025)

FWP Filed Pursuant to Rule 433 Registration Statement (No. 333-291167) November 3, 2025 NiSource Inc. $1,000,000,000 5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated November 3, 2025) This free writing prospectus relates only to the securities described below and should be read together with NiSource Inc.’s prelimina

Security Type

Calculation of Filing Fee Tables S-3 NISOURCE INC. Table 1: Newly Registered and Carry Forward Securities ☐Not Applicable Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry Forward Form Type Carry Forward File Number Carry Forward Initial Effec

Subject to Completion, dated November 3, 2025

424B5 Table of Contents Filed pursuant to Rule 424(b)(5) File No. 333-291167 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted

NiSource announces $1.5 billion at-the-market (ATM) equity issuance program through 2028

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE October 31, 2025 FOR ADDITIONAL INFORMATION Media Investors [email protected] [email protected] NiSource announces $1.5 billion at-the-market (ATM) equity issuance program through 2028 MERRILLVILLE, Ind. - NiSource Inc. (NYSE: NI) (“NiSource”, “we” and “our”) announced today that it has established an “at-the-market” equity offering program under wh

PRIVATE PLACEMENT PROCEDURES

EX-1.2 Exhibit 1.2 To: NiSource Inc. A/C: [   ] From: [Dealer] Re: Issuer Share Forward Sale Transactions Ref. No: [   ] Date: October 31, 2025 Ladies and Gentlemen: The purpose of this communication (this “Master Confirmation”) is to set forth the terms and conditions of the transactions to be entered into from time to time between [   ] (“Dealer”)[, through its agent [   ] (the “Agent”),] and Ni

Security Type

Calculation of Filing Fee Tables S-3 NISOURCE INC. Table 1: Newly Registered and Carry Forward Securities ☐Not Applicable Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry Forward Form Type Carry Forward File Number Carry Forward Initial Effec

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 31, 2025 NiSource Inc. (E

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 31, 2025 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.

Up to $1,500,000,000 NiSource Inc. Common Stock

424B5 Filed pursuant to Rule 424(b)(5) File No. 333-291167 Prospectus Supplement (To Prospectus dated October 30, 2025) Up to $1,500,000,000 NiSource Inc. Common Stock We may issue, offer and sell up to an aggregate of $1,500,000,000 of our common stock, par value $0.01 per share (“common stock”) from time to time through Barclays Capital Inc. (“Barclays”), BMO Capital Markets Corp. (“BMO”), BNP P

NISOURCE INC. COMMON STOCK, PAR VALUE $0.01 PER SHARE EQUITY DISTRIBUTION AGREEMENT October 31, 2025

EX-1.1 Exhibit 1.1 NISOURCE INC. COMMON STOCK, PAR VALUE $0.01 PER SHARE EQUITY DISTRIBUTION AGREEMENT October 31, 2025 October 31, 2025 To: [•] To the Addressees: NiSource Inc., a Delaware corporation (the “Company”), proposes from time to time (i) to issue and sell shares (the “Primary Shares”) of the Company’s common stock, par value $0.01 per share (the “Common Stock”), through [•] (the “Manag

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM T-1 STATEMENT OF ELIGIBILITY UNDER THE TRUST INDENTURE ACT OF 1939 OF A CORPORATION DESIGNATED TO ACT AS TRUSTEE

EX-25.2 Exhibit 25.2 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM T-1 STATEMENT OF ELIGIBILITY UNDER THE TRUST INDENTURE ACT OF 1939 OF A CORPORATION DESIGNATED TO ACT AS TRUSTEE ☐ CHECK IF AN APPLICATION TO DETERMINE ELIGIBILITY OF A TRUSTEE PURSUANT TO SECTION 305(b)(2) THE BANK OF NEW YORK MELLON (Exact name of trustee as specified in its charter) New York 13-516

As Filed with the Securities and Exchange Commission on October 30, 2025

S-3ASR Table of Contents As Filed with the Securities and Exchange Commission on October 30, 2025 Registration No.

Security Type

Calculation of Filing Fee Tables S-3 NISOURCE INC. Table 1: Newly Registered and Carry Forward Securities ☐Not Applicable Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry Forward Form Type Carry Forward File Number Carry Forward Initial Effec

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM T-1 STATEMENT OF ELIGIBILITY UNDER THE TRUST INDENTURE ACT OF 1939 OF A CORPORATION DESIGNATED TO ACT AS TRUSTEE

EX-25.1 Exhibit 25.1 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM T-1 STATEMENT OF ELIGIBILITY UNDER THE TRUST INDENTURE ACT OF 1939 OF A CORPORATION DESIGNATED TO ACT AS TRUSTEE ☐ CHECK IF AN APPLICATION TO DETERMINE ELIGIBILITY OF A TRUSTEE PURSUANT TO SECTION 305(b)(2) THE BANK OF NEW YORK MELLON (Exact name of trustee as specified in its charter) New York 13-516

NISOURCE INC. $[  ] [  ]% [Junior Subordinated][Other Applicable Title of Notes] Notes Due 20[ ] TERMS AGREEMENT

EX-1.2 Exhibit 1.2 NISOURCE INC. (“NiSource”) $[  ] [  ]% [Junior Subordinated][Other Applicable Title of Notes] Notes Due 20[ ] TERMS AGREEMENT [  ], 20[ ] To: [  ] [  ] [  ] [  ] [  ] [  ] [  ] [  ] [  ] [  ] [As Lead Underwriters of the several Underwriters][As Underwriters] The undersigned agrees to sell to [ ], [ ], [ ], [ ] and [ ] (collectively, the “Underwriters”)[, for whom [ ], [ ] and [

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2025 ☐ TRANSITION REPORT PURSUANT

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2025 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Ex

THIRD AMENDED AND RESTATED LIMITED LIABILITY COMPANY AGREEMENT NIPSCO HOLDINGS II LLC

Exhibit 10.2 THIRD AMENDED AND RESTATED LIMITED LIABILITY COMPANY AGREEMENT OF NIPSCO HOLDINGS II LLC 1 Exhibit 10.2 TABLE OF CONTENTS Page ARTICLE I GENERAL MATTERS 2 Section 1.1 Formation 2 Section 1.2 Name 2 Section 1.3 Purpose 2 Section 1.4 Registered Office 2 Section 1.5 Registered Agent 2 Section 1.6 Members 2 Section 1.7 Powers 4 Section 1.8 Limited Liability Company Agreement 4 Section 1.9

AMENDED AND RESTATED LIMITED LIABILITY COMPANY AGREEMENT HOLDINGS II LLC

Exhibit 10.1 AMENDED AND RESTATED LIMITED LIABILITY COMPANY AGREEMENT OF GENERATION HOLDINGS II LLC 1 Exhibit 10.1 TABLE OF CONTENTS Page ARTICLE I GENERAL MATTERS 2 Section 1.1 Formation 2 Section 1.2 Name 2 Section 1.3 Purpose 2 Section 1.4 Registered Office 2 Section 1.5 Registered Agent 2 Section 1.6 Members 3 Section 1.7 Powers 4 Section 1.8 Limited Liability Company Agreement 4 Section 1.9 I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 29, 2025 NiSource Inc. (E

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 29, 2025 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission

NiSource announces third quarter results

Exhibit 99.1 FOR IMMEDIATE RELEASE October 29, 2025 FOR ADDITIONAL INFORMATION Media Investors [email protected] [email protected] NiSource announces third quarter results •Reaffirming upper half of 2025 non-GAAP adjusted EPS guidance •Introducing 2026 non-GAAP consolidated adjusted EPS guidance •Extending base plan expected non-GAAP adjusted EPS annual growth guidance of 6%-8% to 2026-2030

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 22, 2025 NiSource Inc.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 22, 2025 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (

144

144 0001813738 XXXXXXXX LIVE 0001111711 NISOURCE INC. 001-16189 801 EAST 86TH AVE MERRILLVILLE IN 46410-6272 2196475200 Anderson Shawn Officer Common Fidelity Brokerage Services LLC 900 Salem Street Smithfield RI 02917 11115 470497.95 470855009 08/28/2025 NYSE Common 01/24/2025 Restricted Stock Vesting Issuer N 7243 01/24/2025 Compensation Common 02/19/2025 Dividend Reinvestment Issuer N 493 02/19

NiSource announces second quarter results

Exhibit 99.1 FOR IMMEDIATE RELEASE August 6, 2025 FOR ADDITIONAL INFORMATION Media Investors [email protected] [email protected] NiSource announces second quarter results •2025 non-GAAP adjusted EPS guidance narrowed to upper half of range •Reaffirming expected annual 6%-8% 2025-2029 non-GAAP adjusted EPS growth MERRILLVILLE, Ind. - NiSource Inc. (NYSE: NI) today announced, on a GAAP basis,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2025 ☐ TRANSITION REPORT PURSUANT TO S

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2025 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Exact n

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 6, 2025 NiSource Inc. (Exa

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 6, 2025 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission f

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 27, 2025 NiSource Inc. (Exac

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 27, 2025 NiSource Inc. (Exact Name of Registrant as Specified in Charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.R.S.

Exhibit 4.1 to the NiSource Inc. Form 8-K

EX-4.1 Exhibit 4.1 UNLESS THIS GLOBAL NOTE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), NEW YORK, NEW YORK, TO NISOURCE INC. OR ITS AGENT OR AGENTS FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY GLOBAL NOTE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF

Table 1: Newly Registered and Carry Forward Securities

Calculation of Filing Fee Tables S-3 NISOURCE INC. Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry Forward Form Type Carry Forward File Number Carry Forward Initial Effective Date Filing

$1,650,000,000 $900,000,000 5.350% Notes due 2035 $750,000,000 5.850% Notes due 2055

424B2 Table of Contents Filed Pursuant to Rule 424(b)(2) Registration No. 333-268084 Prospectus Supplement (To Prospectus dated November 1, 2022) $1,650,000,000 $900,000,000 5.350% Notes due 2035 $750,000,000 5.850% Notes due 2055 We are offering $1,650,000,000 aggregate principal amount of notes in two series. We are offering $900,000,000 aggregate principal amount of our notes due 2035 (the “203

Subject to Completion, dated June 23, 2025

Table of Contents Filed Pursuant to Rule 424(b)(5), Registration No. 333-268084 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permit

NiSource Inc. $900,000,000 5.350% Notes due 2035 $750,000,000 5.850% Notes due 2055 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated June 23, 2025 (the “Preliminary Prospectus Supplement”)) Issuer: NiSource Inc. Security: 5.350% Notes d

FWP Filed Pursuant to Rule 433 Registration Statement (No. 333-268084) June 23, 2025 NiSource Inc. $900,000,000 5.350% Notes due 2035 $750,000,000 5.850% Notes due 2055 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated June 23, 2025 (the “Preliminary Prospectus Supplement”)) Issuer: NiSource Inc. Security: 5.350% Notes due 2035 (the “ 2035 Notes”) 5.850% Notes due 2055 (the “2055 Note

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 11-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 11-K þ ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024 OR ¨ TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NISOURCE INC. RETIREMENT SAVINGS PLAN

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 12, 2025 NiSource Inc. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 12, 2025 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 ☐ TRANSITION REPORT PURSUANT TO

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Exact

NiSource announces first quarter results

Exhibit 99.1 FOR IMMEDIATE RELEASE May 7, 2025 FOR ADDITIONAL INFORMATION Media Investors Kristen King Investor Relations Finance Communications [email protected] (380) 268-3023 [email protected] NiSource announces first quarter results •Reaffirming 2025 non-GAAP adjusted EPS guidance •Reaffirming expected annual 6%-8% 2025-2029 non-GAAP adjusted EPS growth MERRILLVILLE, Ind. - NiSource Inc.

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 7, 2025 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission file

ARS

MAKING STRIDES. CARRYING MOMENTUM. NISOURCE 2024 ANNUAL REPORTMESSAGE FROM OUR PRESIDENT & CHIEF EXECUTIVE OFFICER MESSAGE FROM OUR CHAIR BOARD OF DIRECTORS AND SENIOR MANAGEMENT TEAM STOCKHOLDER INFORMATION COMPANY INFORMATION 1 4 7 INSIDE BACK COVER BACK COVER WHAT'S INSIDEA MESSAGE FROM OUR PRESIDENT & CHIEF EXECUTIVE OFFICER LLOYD YATES TO OUR SHAREHOLDERS, 2024 was an exceptional year for NiS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   )

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   )         Filed by the Registrant ☒     Filed by a Party other than the Registrant ☐         Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commis

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 27, 2025 NiSource Inc. (Exact Name of Registrant as Specified in Charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.R.S.

Exhibit 4.1 to the NiSource Inc. Form 8-K

Exhibit 4.1 UNLESS THIS GLOBAL NOTE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), NEW YORK, NEW YORK, TO NISOURCE INC. OR ITS AGENT OR AGENTS FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY GLOBAL NOTE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (A

$750,000,000 5.850% Notes due 2055

Table of Contents Filed Pursuant to Rule 424(b)(2) Registration No. 333-268084 Prospectus Supplement (To Prospectus dated November 1, 2022) $750,000,000 5.850% Notes due 2055 We are offering $750,000,000 of our notes due 2055 (the “Notes”). The Notes will bear interest at a rate of 5.850% per year. Interest on the Notes will be paid semi-annually in arrears on April 1 and October 1 of each year, b

Calculation of Filing Fee Table(1) (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charters) Table 1: Newly Registered Securities and Carry Forward Securities

Exhibit 107 Calculation of Filing Fee Table(1) 424(b)(2) (Form Type) NiSource Inc.

NiSource Inc. $750,000,000 5.850% Notes due 2055 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated March 20, 2025) Issuer: NiSource Inc. Security: 5.850% Notes due 2055 (the “Notes”) Ratings (Moody’s; S&P; Fitch)*: Baa2 (stable)/BBB+ (st

Filed Pursuant to Rule 433 Registration Statement (No. 333-268084) March 20, 2025 NiSource Inc. $750,000,000 5.850% Notes due 2055 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated March 20, 2025) Issuer: NiSource Inc. Security: 5.850% Notes due 2055 (the “Notes”) Ratings (Moody’s; S&P; Fitch)*: Baa2 (stable)/BBB+ (stable)/BBB (stable) Size: $750,000,000 Public Offering Price: 99.746%

Subject to Completion, dated March 20, 2025

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-268084 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitt

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☑ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024 ☐ TRANSITION REPORT PURSUANT TO SECTI

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☑ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Exact name

NiSource Inc. Compensation Recoupment Policy.

Exhibit 97.1 NISOURCE INC. COMPENSATION RECOUPMENT POLICY In the event of any required accounting restatement of the financial statements of NiSource Inc. (the “Company”) due to the material noncompliance of the Company with any financial reporting requirement under the applicable U.S. federal securities laws, including any required accounting restatement to correct an error in previously issued f

Securities Transaction Compliance Policy

Exhibit 19.1 POLICY SUBJECT: Securities Transaction Compliance Policy EFFECTIVE DATE: November 2001 REVISED: December 11, 2023 NiSource Inc. (the “Company”) has instituted the following compliance policy in order to protect the Company and assist the Company’s board of directors and all employees in complying with the prohibition against insider trading under Rule 10b-5 under the Securities Exchan

NiSource announces full-year 2024 results

Exhibit 99.1 FOR IMMEDIATE RELEASE: February 12, 2025 NiSource announces full-year 2024 results •Achieved 2024 non-GAAP adjusted EPS above guidance range •Raising 2025 non-GAAP adjusted EPS guidance •Reaffirming expected annual 6%-8% 2025-2029 non-GAAP adjusted EPS growth MERRILLVILLE, Ind. - NiSource Inc. (NYSE: NI) today announced, on a GAAP basis, net income available to common shareholders for

List of Subsidiaries.

Exhibit 21 SUBSIDIARIES OF NISOURCE as of December 31, 2024 Segment/Subsidiary GAS DISTRIBUTION OPERATIONS State of Incorporation Bay State Gas Company Massachusetts Columbia Gas of Kentucky, Inc.

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 12, 2025 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commissio

Description of NiSource Inc.’s Securities Registered Under Section 12 of the Exchange Act.

Exhibit 4.32 DESCRIPTION OF THE REGISTRANT'S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 NiSource Inc. ("NiSource") has one class of securities registered under Section 12 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"): common stock, par value $0.01 per share (the "common stock"). The following is a summary description of the materia

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 22, 2025 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.

Amended and Restated Executive Deferred Compensation Plan, dated August 12, 2024 (filed herewith).

Exhibit 10.1 NISOURCE INC. EXECUTIVE DEFERRED COMPENSATION PLAN Amended and Restated Effective August 12, 2024 TABLE OF CONTENTS Page 1.1 Background 1 1.2 Purpose 1 ARTICLE II DEFINITIONS 2 2.1 Account 2 2.2 Affiliate 2 2.3 Annual Deferral Amount 2 2.4 Beneficiary 2 2.5 Benefits Committee 2 2.6 Board 2 2.7 CHC Committee 2 2.8 Code 2 2.9 Company 3 2.10 Compensation 3 2.11 Discretionary Contribution

Columbia Operations

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2024 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Ex

NiSource announces third quarter 2024 results

Exhibit 99.1 FOR IMMEDIATE RELEASE: October 30, 2024 NiSource announces third quarter 2024 results •Reaffirming 2024 non-GAAP adjusted EPS guidance •Introducing 2025 non-GAAP adjusted EPS guidance and extending expected annual 6-8% growth to 2025-2029 •Updating 5-year capital expenditure base plan to $19.3 billion MERRILLVILLE, Ind. - NiSource Inc. (NYSE: NI) today announced, on a GAAP basis, net

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 30, 2024 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission

Bylaws of NiSource Inc., as amended and restated through October 21, 2024.

Exhibit 3.4 NISOURCE INC. AMENDED AND RESTATED BYLAWS As amended and restated through October 21, 2024 BYLAWS OF NISOURCE INC. ARTICLE I SEAL The corporate seal shall have inscribed thereon the name of the Corporation, the year of its organization and the words “Corporate Seal, Delaware.” The seal may be used by causing it or a facsimile thereof to be impressed or affixed or otherwise reproduced.

Certificate of Elimination of the Company with respect to the Series A Junior Participating Preferred Stock, dated October 21, 2024, issued by NiSource Inc.

Exhibit 3.2 CERTIFICATE OF ELIMINATION OF SERIES A JUNIOR PARTICIPATING PREFERRED STOCK OF NISOURCE INC. Pursuant to Section 151 of the General Corporation Law of the State of Delaware NiSource Inc., a corporation organized and existing under the General Corporation Law of the State of Delaware (the “Corporation”), does hereby certify as follows: 1. Section C of ARTICLE IV of the Corporation’s Cer

Articles of Incorporation of NiSource Inc., as amended and restated through October 21, 2024.

Exhibit 3.3 AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF NISOURCE INC. As Amended Through October 21, 2024 AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF NISOURCE INC. It is hereby certified that: 1. The present name of the corporation (hereinafter the “Corporation”) is NiSource Inc. The Corporation was originally incorporated under the name New NiSource Inc. through its original cer

Certificate of Elimination of the Company with respect to the Series C Preferred Stock, dated October 21, 2024, issued by NiSource Inc.

Exhibit 3.1 CERTIFICATE OF ELIMINATION OF SERIES C MANDATORY CONVERTIBLE PREFERRED STOCK PAR VALUE $0.01 PER SHARE OF NISOURCE INC. Pursuant to Section 151 of the General Corporation Law of the State of Delaware NiSource Inc., a corporation organized and existing under the General Corporation Law of the State of Delaware (the “Corporation”), does hereby certify as follows: 1. At a meeting of the B

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): October 21, 2024 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number)

NI / NiSource Inc. / BlackRock Inc. Passive Investment

us65473p1057091024.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: 16) NISOURCE INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 65473P105 - (CUSIP Number) August 31, 2024 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which

Second Supplemental Indenture, dated as of September 9, 2024, between NiSource Inc. and The Bank of New York Mellon, as trustee

Exhibit 4.2 NISOURCE INC. TO THE BANK OF NEW YORK MELLON Trustee Second Supplemental Indenture Dated as of September 9, 2024 6.375% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2055 TABLE OF CONTENTS Page ARTICLE 1 DEFINITIONS 1 Section 1.1 Defined Terms 1 ARTICLE 2 DESIGNATION OF THE NOTES 3 Section 2.1 Designation and Principal Amount 3 Section 2.2 Form of the Notes 4 Section 2.3 Matu

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 9, 2024 NiSource Inc. (Exact Name of Registrant as Specified in Charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.R

Calculation of Filing Fee Table(1) (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charters) Table 1: Newly Registered Securities and Carry Forward Securities

EX-FILING FEES Calculation of Filing Fee Table(1) 424(b)(2) (Form Type) NiSource Inc.

$500,000,000 6.375% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2055

Filed Pursuant to Rule 424(b)(2) Registration No. 333-268084 Prospectus Supplement (To Prospectus dated November 1, 2022) $500,000,000 6.375% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2055 We are offering $500,000,000 of our 6.375% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2055 (the “Notes”). The Notes will bear interest (i) from and including September 9, 2024 (the “or

NiSource Inc. $500,000,000 6.375% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2055 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated September 3, 2024)

Filed Pursuant to Rule 433 Registration Statement (No. 333-268084) September 3, 2024 NiSource Inc. $500,000,000 6.375% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2055 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated September 3, 2024) This free writing prospectus relates only to the securities described below and should be read together with NiSource Inc.’s preliminary p

Subject to Completion, dated September 3, 2024

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-268084 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitt

As filed with the Securities and Exchange Commission on August 13, 2024

S-8 As filed with the Securities and Exchange Commission on August 13, 2024 Registration No.

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Table Form S-8 (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charter) Newly Registered Securities Note # Security Type Security Class Title Fee Calculation Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee 1 Equity Common Stock, no par value Other 1,300

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2024 ☐ TRANSITION REPORT PURSUANT TO S

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2024 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Exact n

NiSource announces second quarter 2024 results

FOR IMMEDIATE RELEASE: August 7, 2024 NiSource announces second quarter 2024 results •Reaffirming 2024 non-GAAP adjusted EPS guidance •Reaffirming 2023-2028 annual non-GAAP adjusted EPS growth of 6-8% MERRILLVILLE, Ind.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 7, 2024 NiSource Inc. (Exa

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 7, 2024 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission f

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 11-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 11-K þ ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2023 OR ¨ TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NISOURCE INC. RETIREMENT SAVINGS PLAN

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 24, 2024 NiSource Inc. (Exact Name of Registrant as Specified in Charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.R.S.

Form of 5.200% Notes due 2029

Exhibit 4.1 UNLESS THIS GLOBAL NOTE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), NEW YORK, NEW YORK, TO NISOURCE INC. OR ITS AGENT OR AGENTS FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY GLOBAL NOTE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (A

Calculation of Filing Fee Table(1) (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charters) Table 1: Newly Registered Securities and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward

Exhibit 107 Calculation of Filing Fee Table(1) 424(b)(2) (Form Type) NiSource Inc.

$600,000,000 5.200% Notes due 2029

Table of Contents Filed pursuant to Rule 424(b)(2) Registration No. 333-268084 Prospectus Supplement (To Prospectus dated November 1, 2022) $600,000,000 5.200% Notes due 2029 We are offering $600,000,000 of our notes due 2029 (the “Notes”). The Notes will bear interest at a rate of 5.200% per year. Interest on the Notes will be paid semi-annually in arrears on January 1 and July 1 of each year, be

Subject to Completion, dated June 17, 2024

Table of Contents Filed pursuant to Rule 424(b)(5) Registration No. 333-268084 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitt

Subject to Completion, dated June 17, 2024

Table of Contents Filed pursuant to Rule 424(b)(5) Registration No. 333-268084 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitt

NiSource Inc. $600,000,000 5.200% Notes due 2029 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated June 17, 2024) Issuer: NiSource Inc. Security: 5.200% Notes due 2029 (the “Notes”) Ratings (Moody’s; S&P; Fitch)*: Baa2 (stable)/BBB+ (sta

Filed Pursuant to Rule 433 Registration Statement (No. 333-268084) June 17, 2024 NiSource Inc. $600,000,000 5.200% Notes due 2029 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated June 17, 2024) Issuer: NiSource Inc. Security: 5.200% Notes due 2029 (the “Notes”) Ratings (Moody’s; S&P; Fitch)*: Baa2 (stable)/BBB+ (stable)/BBB (stable) Size: $600,000,000 Public Offering Price: 99.798% o

Subordinated Indenture, dated as of May 16, 2024, between NiSource Inc. and The Bank of New York Mellon, as trustee

Exhibit 4.2 Execution Version NISOURCE INC. to THE BANK OF NEW YORK MELLON as Trustee INDENTURE Dated as of May 16, 2024 Providing for Issuance of Subordinated Debt Securities NiSource Inc. Reconciliation and Tie between Trust Indenture Act of 1939, as amended, and Indenture, dated as of May 16, 2024 Trust Indenture Act Section Indenture Section(s) §310 (a)(1) 609    (a)(2) 609    (a)(3)       Not

First Supplemental Indenture, dated as of May 16, 2024, between NiSource Inc. and The Bank of New York Mellon, as trustee

Exhibit 4.3 NISOURCE INC. TO THE BANK OF NEW YORK MELLON Trustee First Supplemental Indenture Dated as of May 16, 2024 6.950% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2054 TABLE OF CONTENTS Page ARTICLE 1 DEFINITIONS 1 Section 1.1 Defined Terms 1 ARTICLE 2 DESIGNATION OF THE NOTES 3 Section 2.1 Designation and Principal Amount 3 Section 2.2 Form of the Notes 4 Section 2.3 Maturity D

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 16, 2024 NiSource Inc. (Exact Name of Registrant as Specified in Charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.R.S. E

Calculation of Filing Fee Table(1) (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charters) Table 1: Newly Registered Securities and Carry Forward Securities

Exhibit 107 Calculation of Filing Fee Table(1) 424(b)(2) (Form Type) NiSource Inc.

$500,000,000 6.950% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2054

Table of Contents Filed Pursuant to Rule 424(b)(2) Registration No. 333-268084 Prospectus Supplement (To Prospectus dated November 1, 2022) $500,000,000 6.950% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2054 We are offering $500,000,000 of our 6.950% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2054 (the “Notes”). The Notes will bear interest (i) from and including the orig

NiSource Inc. $500,000,000 6.950% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2054 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated May 13, 2024)

Filed Pursuant to Rule 433 Registration Statement (No. 333-268084) May 13, 2024 NiSource Inc. $500,000,000 6.950% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2054 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated May 13, 2024) This free writing prospectus relates only to the securities described below and should be read together with NiSource Inc.’s preliminary prospectus

Subject to Completion, dated May 13, 2024

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-268084 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitt

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 13, 2024 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 8, 2024 NiSource Inc. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 8, 2024 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission file

NiSource announces first quarter 2024 results

Exhibit 99.1 FOR IMMEDIATE RELEASE: May 8, 2024 NiSource announces first quarter 2024 results •Reaffirming 2024 non-GAAP adjusted EPS guidance •Reaffirming 2023-2028 annual non-GAAP adjusted EPS growth of 6-8% MERRILLVILLE, Ind. - NiSource Inc. (NYSE: NI) today announced, on a GAAP basis, net income available to common shareholders for the three months ended March 31, 2024, of $344.3 million, or $

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 ☐ TRANSITION REPORT PURSUANT TO

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Exact

NiSource Inc. (NI)

NiSource Inc. (NI) Shareholder Alert Voluntary submission by John Chevedden, POB 2673, Redondo Beach, CA 90278 NiSource Shareholder since 2017 Important to Vote for Shareholder Say on Director Pay – Proposal 5 There is no greater conflict of interest than when a Board approves its own pay, with no oversight from the shareholders whose interest they must represent above their own. This proposal rec

ARS

Driving Consistent Execution, Growth and Value NISOURCE 2023 ANNUAL REPORTMESSAGE FROM OUR PRESIDENT & CHIEF EXECUTIVE OFFICER MESSAGE FROM OUR CHAIR BOARD OF DIRECTORS, SENIOR MANAGEMENT TEAM AND DIVERSITY STATS SCHEDULE 1 STOCKHOLDER INFORMATION COMPANY INFORMATION 1 4 7 8 INSIDE BACK COVER BACK COVER What’s InsideA MESSAGE FROM OUR PRESIDENT & CHIEF EXECUTIVE OFFICER Lloyd Yates As a trusted energy partner, we are committed to putting our shareholders, customers, employees and the communities we serve at the forefront of everything we do.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   )

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permit

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(

Aristides S. Candris Departs from the Board After 12 Years of Service

Exhibit 99.1 FOR IMMEDIATE RELEASE: March 19, 2024 Aristides S. Candris Departs from the Board After 12 Years of Service NiSource Inc. (NYSE: NI) today announced Aristides S. Candris, who has served as a director since 2012, has retired from the NiSource Board, and that it has appointed John McAvoy to its Board of Directors, effective immediately. “We are pleased with the appointment of John McAvo

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 18, 2024 NiSource Inc. (Exact name of registrant as specified in its charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 18, 2024 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (

Certificate of Elimination of the Company with respect to the Series B Preferred Stock and the Series B-1 Preferred Stock, dated March 18, 2024, issued by NiSource Inc.

Exhibit 3.1 CERTIFICATE OF ELIMINATION OF 6.50% SERIES B FIXED-RATE RESET CUMULATIVE REDEEMABLE PERPETUAL PREFERRED STOCK AND SERIES B-1 PREFERRED STOCK OF NISOURCE INC. Pursuant to Section 151 of the General Corporation Law of the State of Delaware NiSource Inc., a corporation organized and existing under the General Corporation Law of the State of Delaware (the “Corporation”), does hereby certif

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 15, 2024 NiSource Inc. (Exa

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 15, 2024 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.R.

Separation Agreement dated March 15, 2024, between NiSource Inc. and Donald Brown

EX-10.1 Exhibit 10.1 SEPARATION AGREEMENT AND FULL RELEASE AND WAIVER OF CLAIMS This Confidential Separation Agreement and Full Release and Waiver of Claims (“Agreement”) is entered into by and between Donald Brown (“Employee” or “you/your”) and NiSource Corporate Services Company (“NiSource” or “the Company”) (collectively, “the Parties”). In consideration of the mutual promises, covenants, and a

EX-99.25

NOTIFICATION OF THE REMOVAL FROM LISTING AND REGISTRATION OF THE STATED SECURITIES The New York Stock Exchange hereby notifies the SEC of its intention to remove the entire class of the stated securities from listing and registration on the Exchange at the opening of business on March 26, 2024, pursuant to the provisions of Rule 12d2-2 (a).

Form of 5.350% Notes due 2034

EX-4.1 Exhibit 4.1 UNLESS THIS GLOBAL NOTE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), NEW YORK, NEW YORK, TO NISOURCE INC. OR ITS AGENT OR AGENTS FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY GLOBAL NOTE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 14, 2024 NiSource Inc. (Exa

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 14, 2024 NiSource Inc. (Exact Name of Registrant as Specified in Charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.R.S.

$650,000,000 5.350% Notes due 2034

Table of Contents Filed pursuant to Rule 424(b)(2) File No. 333-268084 Prospectus Supplement (To Prospectus dated November 1, 2022) $650,000,000 5.350% Notes due 2034 We are offering $650,000,000 of our notes due 2034 (the “Notes”). The Notes will bear interest at a rate of 5.350% per year. Interest on the Notes will be paid semi-annually in arrears on April 1 and October 1 of each year, beginning

Calculation of Filing Fee Table(1) (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charters) Table 1: Newly Registered Securities and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward

Exhibit 107 Calculation of Filing Fee Table(1) 424(b)(2) (Form Type) NiSource Inc.

Subject to Completion, dated March 11, 2024

Table of Contents Filed pursuant to Rule 424(b)(5) File No. 333-268084 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted. Subj

NiSource Inc. $650,000,000 5.350% Notes due 2034 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated March 11, 2024) Issuer: NiSource Inc. Security: 5.350% Notes due 2034 (the “Notes”) Ratings (Moody’s; S&P; Fitch)*: Baa2 (stable)/BBB+ (st

Filed Pursuant to Rule 433 Registration Statement (No. 333-268084) March 11, 2024 NiSource Inc. $650,000,000 5.350% Notes due 2034 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated March 11, 2024) Issuer: NiSource Inc. Security: 5.350% Notes due 2034 (the “Notes”) Ratings (Moody’s; S&P; Fitch)*: Baa2 (stable)/BBB+ (stable)/BBB (stable) Size: $650,000,000 Public Offering Price: 99.781%

NiSource Announces Two-Year $900 Million At-The-Market (ATM) Equity Issuance Program

Exhibit 99.1 FOR IMMEDIATE RELEASE: February 22, 2024 NiSource Announces Two-Year $900 Million At-The-Market (ATM) Equity Issuance Program MERRILLVILLE, Ind. – NiSource Inc. (NYSE: NI) (“NiSource”) announced today that it has established an “at-the-market” (“ATM”) equity offering program under which it may sell shares of its common stock having an aggregate gross sales price of up to $900 million

Form of Master Forward Sale Confirmation

Exhibit 1.2 To: NiSource Inc. A/C: [   ] From: [Dealer] Re: Issuer Share Forward Sale Transactions Ref. No: [   ] Date: February 22, 2024 Ladies and Gentlemen: The purpose of this communication (this “Master Confirmation”) is to set forth the terms and conditions of the transactions to be entered into from time to time between [    ] (“Dealer”)[, through its agent [    ] (the “Agent”),] and NiSour

Calculation of Filing Fee Table(1) (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charters) Table 1: Newly Registered Securities and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward

EX-FILING FEES Exhibit 107 Calculation of Filing Fee Table(1) 424(b)(5) (Form Type) NiSource Inc.

Entry into a Material Definitive Agreement, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 22, 2024 NiSource Inc. (Exact Name of Registrant as Specified in Charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.R

Form of Equity Distribution Agreement

Exhibit 1.1 NISOURCE INC. COMMON STOCK, PAR VALUE $0.01 PER SHARE EQUITY DISTRIBUTION AGREEMENT February 22, 2024 February 22, 2024 To: [•] To the Addressees: NiSource Inc., a Delaware corporation (the “Company”), proposes from time to time (i) to issue and sell shares (the “Primary Shares”) of the Company’s common stock, par value $0.01 per share (the “Common Stock”), through [•] (the “Manager”),

Up to $900,000,000 NiSource Inc. Common Stock

424B5 Table of Contents Filed pursuant to Rule 424(b)(5) File No. 333-268084 Prospectus Supplement (To Prospectus dated November 1, 2022) Up to $900,000,000 NiSource Inc. Common Stock We may issue, offer and sell up to an aggregate of $900,000,000 of our common stock, par value $0.01 per share (“common stock”) from time to time through Barclays Capital Inc. (“Barclays”), BMO Capital Markets Corp.

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 21, 2024 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commissio

Form of PSU Award Agreement (for award

Exhibit 10.48 NiSource Inc. 2020 Omnibus Incentive Plan 202[ ] Performance Share Unit Award Agreement This Performance Share Unit Award Agreement (the “Agreement”) is made and entered into as of [DATE] (the “Grant Date”), by and between NiSource Inc., a Delaware corporation (the “Company”), and [NAME], an Employee of the Company or an Affiliate (the “Grantee”), pursuant to the terms of the NiSourc

List of Subsidiaries.

Exhibit 21 SUBSIDIARIES OF NISOURCE as of December 31, 2023 Segment/Subsidiary GAS DISTRIBUTION OPERATIONS State of Incorporation Bay State Gas Company d/b/a Columbia Gas of Massachusetts Massachusetts Columbia Gas of Kentucky, Inc.

Description of NiSource Inc.’s Securities Registered Under Section 12 of the Exchange Act.

Exhibit 4.25 DESCRIPTION OF THE REGISTRANT'S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 NiSource Inc. ("NiSource") has two classes of securities registered under Section 12 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"): (i)common stock, par value $0.01 per share (the "common stock"); and (ii)depositary shares, each representing a 1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☑ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2023 ☐ TRANSITION REPORT PURSUANT TO SECTI

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☑ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Exact name

NiSource announces fourth quarter 2023 results

Exhibit 99.1 FOR IMMEDIATE RELEASE: February 21, 2024 NiSource announces fourth quarter 2023 results •Achieved 2023 non-GAAP NOEPS at top end of guidance range •Raising 2024 non-GAAP NOEPS guidance to $1.70-1.74 from $1.68-1.72 •Reaffirming 6-8% annual 2023-2028 non-GAAP NOEPS growth •Successfully closed NIPSCO minority interest transaction in December MERRILLVILLE, Ind. - NiSource Inc. (NYSE: NI)

NiSource Inc. Compensation Recoupment Policy.

Exhibit 97.1 NISOURCE INC. COMPENSATION RECOUPMENT POLICY In the event of any required accounting restatement of the financial statements of NiSource Inc. (the “Company”) due to the material noncompliance of the Company with any financial reporting requirement under the applicable U.S. federal securities laws, including any required accounting restatement to correct an error in previously issued f

First Amendment to the Savings Restoration Plan for NiSource Inc. and Affiliates dated October 12, 2023 and effective November 1, 2020.

Exhibit 10.24 FIRST AMENDMENT TO THE SAVINGS RESTORATION PLAN FOR NISOURCE INC. AND AFFILIATES (AMENDED AND RESTATED EFFECTIVE NOVEMBER 1, 2020) BACKGROUND A. NiSource Inc. (the “Company”) maintains the Savings Restoration Plan for NiSource Inc. and Affiliates, amended and restated effective November 1, 2020 (the “Plan”). B. The Company desires to amend the Plan to increase the amount of the Next-

Second Amended and Restated Limited Liability Company Agreement of NIPSCO Holdings II LLC, dated January 30, 2024.

Exhibit 10.44 SECOND AMENDED AND RESTATED LIMITED LIABILITY COMPANY AGREEMENT OF NIPSCO HOLDINGS II LLC TABLE OF CONTENTS Page Article I GENERAL MATTERS iv Section 1.1 Formation iv Section 1.2 Name iv Section 1.3 Purpose iv Section 1.4 Registered Office v Section 1.5 Registered Agent v Section 1.6 Members v Section 1.7 Powers vi Section 1.8 Limited Liability Company Agreement vi Section 1.9 Issuan

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 19, 2024 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I

NI / NiSource Inc. / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 15)* Name of issuer: NiSource Inc Title of Class of Securities: Common Stock CUSIP Number: 65473P105 Date of Event Which Requires Filing of this Statement: December 29, 2023 Check the appropriate box to designate the rule pursuant to which this Schedule is filed: ☒ Rule

NiSource Inc. Announces Redemption of All Depositary Shares Representing Interests in Its 6.50% Series B Fixed-Rate Reset Cumulative Redeemable Perpetual Preferred Stock and Series B-1 Preferred Stock

Exhibit 99.1 FOR IMMEDIATE RELEASE: February 9, 2024 NiSource Inc. Announces Redemption of All Depositary Shares Representing Interests in Its 6.50% Series B Fixed-Rate Reset Cumulative Redeemable Perpetual Preferred Stock and Series B-1 Preferred Stock MERRILLVILLE, Ind. - NiSource Inc. (NYSE: NI) (“NiSource”) announced today that it will redeem all outstanding shares of its 6.50% Series B Fixed-

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 9, 2024 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number)

NI / NiSource Inc. / STATE STREET CORP Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 AMENDED FILING NISOURCE INC (NAME OF ISSUER) COMMON STOCK (TITLE OF CLASS OF SECURITIES) 65473P105 (CUSIP NUMBER) 12/31/2023 (DATE OF EVENT WHICH REQUIRES FILING OF THIS STATEMENT) CHECK THE APPROPRIATE BOX TO DESIGNATE THE RULE PURSUANT TO WHICH THIS SCHEDULE IS FILED: (X

Exhibit 10.1 of the NiSource Inc. Form 8-K

Exhibit 10.1 CEO NiSource Inc. 2020 Omnibus Incentive Plan 202[ ] Restricted Stock Unit Award Agreement This Restricted Stock Unit Award Agreement (the “Agreement”), is made and entered into as of [DATE] (the “Grant Date”), by and between NiSource Inc., a Delaware corporation (the “Company”), and [NAME], an Employee of the Company or an Affiliate (the “Grantee”), pursuant to the terms of the NiSou

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 24, 2024 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.

Exhibit 10.3 of the NiSource Inc. Form 8-K

Exhibit 10.3 NiSource Inc. 2020 Omnibus Incentive Plan 202[ ] [Special] Restricted Stock Unit Award Agreement This [Special] Restricted Stock Unit Award Agreement (the “Agreement”), is made and entered into as of [DATE] (the “Grant Date”), by and between NiSource Inc., a Delaware corporation (the “Company”), and [NAME], an Employee of the Company or an Affiliate (the “Grantee”), pursuant to the te

Exhibit 10.2 of the NiSource Inc. Form 8-K

Exhibit 10.2 CEO NiSource Inc. 2020 Omnibus Incentive Plan 202[ ] Performance Share Unit Award Agreement This Performance Share Unit Award Agreement (the “Agreement”) is made and entered into as of [DATE] (the “Grant Date”), by and between NiSource Inc., a Delaware corporation (the “Company”), and [NAME], an Employee of the Company or an Affiliate (the “Grantee”), pursuant to the terms of the NiSo

NI / NiSource Inc. / BlackRock Inc. Passive Investment

SC 13G/A 1 us65473p1057012424.txt us65473p1057012424.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: 15) NISOURCE INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 65473P105 - (CUSIP Number) December 31, 2023 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to d

Exhibit 10.1 of the NiSource Inc. Form 8-K

Exhibit 10.1 Execution Version AMENDED AND RESTATED LIMITED LIABILITY COMPANY AGREEMENT OF NIPSCO HOLDINGS II LLC TABLE OF CONTENTS Page ARTICLE I GENERAL MATTERS 1 Section 1.1 Formation 1 Section 1.2 Name 1 Section 1.3 Purpose 1 Section 1.4 Registered Office 2 Section 1.5 Registered Agent 2 Section 1.6 Members 2 Section 1.7 Powers 3 Section 1.8 Limited Liability Company Agreement 3 Section 1.9 Is

Regulation FD Disclosure, Entry into a Material Definitive Agreement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 31, 2023 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number

NiSource Inc. Completes NIPSCO Minority Equity Interest Transaction

Exhibit 99.1 FOR IMMEDIATE RELEASE: January 2, 2024 NiSource Inc. Completes NIPSCO Minority Equity Interest Transaction • Investment by Blackstone Infrastructure Partners affiliate (“Blackstone”) to acquire a 19.9% indirect non-controlling equity interest in NIPSCO for $2.16 billion, with an additional equity commitment of $250 million to fund ongoing capital requirements, strengthens NIPSCO’s fin

Entry into a Material Definitive Agreement, Material Modification to Rights of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 18, 2023 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number

Exhibit 10.1 to the NiSource Inc. Form 8-K

Exhibit 10.1 Execution Version FOURTH SUPPLEMENTAL INDENTURE FOURTH SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), dated as of December 18, 2023, between NiSource Inc., a Delaware corporation (“NiSource”), and The Bank of New York Mellon, a New York banking corporation, not in its individual capacity but solely as successor trustee (the “Trustee”) under the Indenture dated as of February

Exhibit 10.1 to the NiSource Inc. Form 8-K

EX-10.1 Exhibit 10.1 EXECUTION COPY AUGMENTING LENDER SUPPLEMENT AUGMENTING LENDER SUPPLEMENT, dated December 6, 2023 (this “Supplement”), by and among each of the signatories hereto, to the Credit Agreement dated as of November 9, 2023 (as amended, restated, supplemented or otherwise modified from time to time, the “Credit Agreement”), between NiSource Inc., a Delaware corporation (the “Borrower”

Entry into a Material Definitive Agreement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 6, 2023 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number)

Regulation FD Disclosure, Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 1, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.

EX-99.25

NOTIFICATION OF THE REMOVAL FROM LISTING AND REGISTRATION OF THE STATED SECURITIES The New York Stock Exchange hereby notifies the SEC of its intention to remove the entire class of the stated securities from listing and registration on the Exchange at the opening of business on December 12, 2023, pursuant to the provisions of Rule 12d2-2 (a).

NiSource Inc. Announces the Settlement Rate for the Purchase Contract Component of its 2021 Equity Units Offering

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE: December 1, 2023 NiSource Inc. Announces the Settlement Rate for the Purchase Contract Component of its 2021 Equity Units Offering MERRILLVILLE, Ind. – NiSource Inc. (NYSE: NI) (“NiSource”) announced today the settlement rate of the purchase contracts that form part of its Series A Corporate Units (the “Corporate Units”), originally issued on April 19, 2

###

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE: November 17, 2023 NiSource Inc. Announces Results of Final Remarketing of its Series C Mandatory Convertible Preferred Stock Relating to its 2021 Equity Units Offering MERRILLVILLE, Ind. – NiSource Inc. (NYSE: NI) (“NiSource”) announced today the unsuccessful final remarketing of its Series C Mandatory Convertible Preferred Stock, par value $0.01 per sha

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 17, 2023 NiSource Inc. (

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 17, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 17, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I

NiSource Inc. Announces Postponement of the Final Remarketing of its Series C Mandatory Convertible Preferred Stock

Exhibit 99.1 FOR IMMEDIATE RELEASE: November 15, 2023 NiSource Inc. Announces Postponement of the Final Remarketing of its Series C Mandatory Convertible Preferred Stock MERRILLVILLE, Ind. – NiSource Inc. (NYSE: NI) (“NiSource”) is announcing that it has postponed, at its option, the final remarketing of 862,500 shares of its Series C Mandatory Convertible Preferred Stock, par value $0.01 per shar

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 15, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I

Consistent With its Long-Term Financial Plan NiSource Inc. Announces Commencement of Final Remarketing of its Series C Mandatory Convertible Preferred Stock Relating to its 2021 Equity Units Offering

Exhibit 99.1 FOR IMMEDIATE RELEASE: November 14, 2023 Consistent With its Long-Term Financial Plan NiSource Inc. Announces Commencement of Final Remarketing of its Series C Mandatory Convertible Preferred Stock Relating to its 2021 Equity Units Offering MERRILLVILLE, Ind. – In accordance with NiSource’s long-term financial plan, NiSource Inc. (NYSE: NI) (“NiSource”) announced today the commencemen

SUBJECT TO COMPLETION PRELIMINARY PROSPECTUS SUPPLEMENT DATED NOVEMBER 14, 2023

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-268084 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not offers to sell nor solicitations of offers to buy these securities in any jurisdiction where the offer or sale is not permitted. SUBJECT TO COMPLETI

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 14, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I

Exhibit 10.1 to the NiSource Inc. Form 8-K

Exhibit 10.1 EXECUTION COPY CREDIT AGREEMENT among NISOURCE INC., as Borrower, THE LENDERS PARTY HERETO, and U.S. BANK NATIONAL ASSOCIATION, as Administrative Agent, U.S. BANK NATIONAL ASSOCIATION, as Sole Lead Arranger and Bookrunner Dated as of November 9, 2023 TABLE OF CONTENTS Page ARTICLE I DEFINITIONS 1 SECTION 1.01. DEFINED TERMS 1 SECTION 1.02. CLASSIFICATION OF LOANS AND BORROWINGS 22 SEC

Entry into a Material Definitive Agreement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 9, 2023 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 ☐ TRANSITION REPORT PURSUANT

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Ex

NiSource announces third quarter 2023 results, extension to long-term growth plan

Exhibit 99.1 FOR IMMEDIATE RELEASE: November 1, 2023 NiSource announces third quarter 2023 results, extension to long-term growth plan •Reaffirming 2023 non-GAAP NOEPS guidance in upper half of the range •Introducing 2024 non-GAAP NOEPS guidance and extending annual 6-8% growth from 2023-28 •NIPSCO minority interest transaction with Blackstone Infrastructure Partners on-track for closing by the en

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 1, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission

NiSource Inc. announces Federal Energy Regulatory Commission approval of sale of 19.9% equity interest in NIPSCO

Exhibit 99.1 FOR IMMEDIATE RELEASE: October 19, 2023 NiSource Inc. announces Federal Energy Regulatory Commission approval of sale of 19.9% equity interest in NIPSCO MERRILLVILLE, Ind. – NiSource Inc. (NYSE: NI) (“NiSource”) announced today the Federal Energy Regulatory Commission (FERC) granted approval of the acquisition of a 19.9% equity interest in the company’s Northern Indiana Public Service

Consistent With its Long-Term Financial Plan NiSource Inc. Announces Final Remarketing Period of its Series C Mandatory Convertible Preferred Stock Relating to its 2021 Equity Units Offering

Exhibit 99.1 FOR IMMEDIATE RELEASE: October 20, 2023 Consistent With its Long-Term Financial Plan NiSource Inc. Announces Final Remarketing Period of its Series C Mandatory Convertible Preferred Stock Relating to its 2021 Equity Units Offering MERRILLVILLE, Ind. – NiSource Inc. (NYSE: NI) (“NiSource”) announced today the period beginning on November 13, 2023 and ending on November 17, 2023 as the

Regulation FD Disclosure

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 19, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.

Regulation FD Disclosure

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 20, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.

Exhibit 10.1 to the NiSource Inc. Form 8-K

Exhibit 10.1 EXECUTION COPY AMENDMENT NO. 1 TO CREDIT AGREEMENT Dated as of October 5, 2023 THIS AMENDMENT NO. 1 TO CREDIT AGREEMENT (this “Amendment”) is made as of October 5, 2023, by and among NiSource Inc., a Delaware corporation (the “Borrower”), the financial institutions listed on the signature pages hereof and JPMorgan Chase Bank, N.A., as administrative agent (the “Administrative Agent”),

Entry into a Material Definitive Agreement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): October 5, 2023 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number)

NiSource Inc. Announces Decision to Postpone the Remarketing of its Series C Mandatory Convertible Preferred Stock Due to Market

Exhibit 99.1 FOR IMMEDIATE RELEASE: September 28, 2023 NiSource Inc. Announces Decision to Postpone the Remarketing of its Series C Mandatory Convertible Preferred Stock Due to Market Conditions MERRILLVILLE, Ind. – NiSource Inc. (NYSE: NI) (“NiSource”) announced today that due to market conditions it has decided to postpone at its option the remarketing of up to 862,500 shares of its Series C Man

Regulation FD Disclosure

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 28, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 15, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (

Consistent With its Long-Term Financial Plan NiSource Inc. Announces its Intention to Remarket the Series C Mandatory Convertible Preferred Stock Relating to its 2021 Equity Units Offering

Exhibit 99.1 FOR IMMEDIATE RELEASE: September 15, 2023 Consistent With its Long-Term Financial Plan NiSource Inc. Announces its Intention to Remarket the Series C Mandatory Convertible Preferred Stock Relating to its 2021 Equity Units Offering MERRILLVILLE, Ind. – NiSource Inc. (NYSE: NI) (“NiSource”) announced today its intention to remarket, subject to market and other conditions, up to 862,500

Exhibit 10.1 to the NiSource Inc. Form 8-K

Exhibit 10.1 EXECUTION COPY AMENDMENT NO. 1 Dated as of August 23, 2023 to SIXTH AMENDED AND RESTATED REVOLVING CREDIT AGREEMENT Dated as of February 18, 2022 THIS AMENDMENT NO. 1 (this “Amendment”) is made as of August 23, 2023 by and among NiSource Inc., a Delaware corporation (the “Borrower”), the financial institutions listed on the signature pages hereof and Barclays Bank PLC, as administrati

Entry into a Material Definitive Agreement, Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 23, 2023 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number)

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 2, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission f

Exhibit 10.2 of the NiSource Inc. Form 10-Q

Exhibit 10.2 Execution Version AMENDMENT NO. 1 TO PURCHASE AND SALE AGREEMENT THIS AMENDMENT NO. 1 TO PURCHASE AND SALE AGREEMENT (this “Amendment”) is made as of the July 6, 2023 by and among NiSource Inc., a Delaware corporation (the “Parent”), NIPSCO Holdings II LLC, a Delaware limited liability company (the “Company”), and BIP Blue Buyer L.L.C., a Delaware limited liability company (the “Inves

NiSource announces second quarter 2023 results

Exhibit 99.1 FOR IMMEDIATE RELEASE: August 2, 2023 NiSource announces second quarter 2023 results •2023 EPS guidance raised to upper half of range, long-term growth commitments reaffirmed •Leading regulatory execution continues in both electric and gas businesses •NIPSCO minority sale agreement with Blackstone Infrastructure Partners announced, expected to close by year-end MERRILLVILLE, Ind. - Ni

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 ☐ TRANSITION REPORT PURSUANT TO S

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Exact n

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 11-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 11-K þ ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2022 OR ¨ TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NISOURCE INC. RETIREMENT SAVINGS PLAN

Exhibit 10.1 to the NiSource Inc. Form 8-K

EX-10.1 Exhibit 10.1 Execution Version PURCHASE AND SALE AGREEMENT dated as of June 17, 2023 by and among NISOURCE INC., NIPSCO HOLDINGS II LLC and BIP BLUE BUYER L.L.C. TABLE OF CONTENTS Page ARTICLE I PURCHASE AND SALE TRANSACTION; PURCHASE PRICE; THE CLOSING 1 Section 1.1 Purchase and Sale 1 Section 1.2 Purchase Price 2 Section 1.3 Closing 4 Section 1.4 The Closing Transactions 4 ARTICLE II REP

NiSource Announces Agreement to Sell Minority Equity Interest in NIPSCO to Strengthen Financial Foundation and Support Sustainable, Long-Term Growth Blackstone Infrastructure Partners Affiliate Agrees to Acquire 19.9% Non-Controlling Equity Interest

EX-99.1 Exhibit 99.1 NiSource Announces Agreement to Sell Minority Equity Interest in NIPSCO to Strengthen Financial Foundation and Support Sustainable, Long-Term Growth Blackstone Infrastructure Partners Affiliate Agrees to Acquire 19.9% Non-Controlling Equity Interest in NIPSCO for $2.150 Billion, with Additional Equity Commitment of $250 Million to Fund Ongoing Capital Requirements Blackstone I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): June 17, 2023 NiSource Inc. (Exac

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): June 17, 2023 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Material Modification to Rights of Security Holders, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 16, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.R.S

Certificate of Elimination of the Company with respect to the Series A Preferred Stock, dated June 16, 2023

EX-3.1 Exhibit 3.1 CERTIFICATE OF ELIMINATION OF 5.65% SERIES A FIXED-RATE RESET CUMULATIVE REDEEMABLE PERPETUAL PREFERRED STOCK OF NISOURCE INC. Pursuant to Section 151 of the General Corporation Law of the State of Delaware NiSource Inc., a corporation organized and existing under the General Corporation Law of the State of Delaware (the “Corporation”), does hereby certify as follows: 1. At a me

NiSource Closes on Bond Offering

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE: June 8, 2023 NiSource Closes on Bond Offering MERRILLVILLE, Ind. - NiSource Inc. (NYSE: NI) (“NiSource”) closed today on its issuance of $750 million aggregate principal amount of notes in two series. NiSource issued an additional $300 million of its 5.250% notes due March 30, 2028. The 5-year senior, unsecured notes priced at 100.280% of the incremental

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 8, 2023 NiSource Inc. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 8, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.R.S.

Exhibit 4.2 to the NiSource Inc. Form 8-K

EX-4.2 Exhibit 4.2 UNLESS THIS GLOBAL NOTE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), NEW YORK, NEW YORK, TO NISOURCE INC. OR ITS AGENT OR AGENTS FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY GLOBAL NOTE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF

Calculation of Filing Fee Tables Form S-3 (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule

Exhibit 107 Calculation of Filing Fee Tables Form S-3 (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry For

$750,000,000 $300,000,000 5.250% Notes due 2028 $450,000,000 5.400% Notes due 2033

424B2 Table of Contents Filed Pursuant to Rule 424(b)(2) Registration No. 333-268084 Prospectus Supplement (To Prospectus dated November 1, 2022) $750,000,000 $300,000,000 5.250% Notes due 2028 $450,000,000 5.400% Notes due 2033 We are offering $750,000,000 aggregate principal amount of notes in two series. We are offering $300,000,000 of our notes due 2028 (the “2028 Notes”) and $450,000,000 of o

Subject to Completion, dated May 30, 2023

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-268084 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitt

NiSource Inc. $300,000,000 5.250% Notes due 2028 $450,000,000 5.400% Notes due 2033 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated May 30, 2023) Issuer: NiSource Inc. Security: 5.250% Notes due 2028 (the “2028 Notes”) 5.400% Notes due

Filed Pursuant to Rule 433 Registration Statement (No. 333-268084) May 30, 2023 NiSource Inc. $300,000,000 5.250% Notes due 2028 $450,000,000 5.400% Notes due 2033 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated May 30, 2023) Issuer: NiSource Inc. Security: 5.250% Notes due 2028 (the “2028 Notes”) 5.400% Notes due 2033 (the “2033 Notes”) Ratings (Moody’s; S&P; Fitch)*: Baa2 (stable)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 23, 2023 NiSource Inc. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 23, 2023 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number) (I.

Certificate of Amendment of Amended and Restated Certificate of Incorporation of NiSource dated May 23, 2023 (incorporated by reference to Exhibit 3.1 of the NiSource Inc. Form 8-K filed on May 24, 2023).

EX-3.1 Exhibit 3.1 STATE OF DELAWARE CERTIFICATE OF AMENDMENT OF AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF NISOURCE INC. NiSource Inc. (the “Corporation”), a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware, does hereby certify: FIRST: that this Certificate of Amendment amends the provisions of the Corporation’s Amended and R

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 8, 2023 NiSource Inc. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 8, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.R.S.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 3, 2023 NiSource Inc. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 3, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission file

NiSource announces first quarter 2023 results

FOR IMMEDIATE RELEASE: May 3, 2023 NiSource announces first quarter 2023 results •2023 guidance and long-term growth commitments reaffirmed •Regulatory progress continues with a NIPSCO electric rate case settlement that provides a balanced outcome for stakeholders •NIPSCO minority interest sale launched and on track for 2023 MERRILLVILLE, Ind.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 ☐ TRANSITION REPORT PURSUANT TO

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Exact

Definitive Proxy Statement

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permit

ARS

An innovative and trusted energy partner 2022 INTEGRATED ANNUAL REPORTSafety | Sustainability | Customers | Employees Excellence | Financial This report shows how we are living the refreshed VISION we adopted in 2022.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. 1)

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. 1) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitt

NiSource Closes on Bond Offering

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE: March 24, 2023 NiSource Closes on Bond Offering MERRILLVILLE, Ind.—NiSource Inc. (NYSE: NI) (“NiSource”) closed today on its issuance of $750 million principal amount of notes due March 30, 2028. The 5-year senior, unsecured notes priced at 99.829% of the aggregate principal amount, with a coupon rate of 5.25%. The notes will accrue interest payable semi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 24, 2023 NiSource Inc. (Exa

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 24, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number (I.R.

Exhibit 4.1 to the NiSource Inc. Form 8-K

EX-4.1 Exhibit 4.1 UNLESS THIS GLOBAL NOTE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), NEW YORK, NEW YORK, TO NISOURCE INC. OR ITS AGENT OR AGENTS FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY GLOBAL NOTE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF

$750,000,000 5.250% Notes due 2028

424B2 Table of Contents Filed Pursuant to Rule 424(b)(2) Registration No. 333-268084 Prospectus Supplement (To Prospectus dated November 1, 2022) $750,000,000 5.250% Notes due 2028 The notes will mature on March 30, 2028 (the “Notes”). The Notes will bear interest at a rate of 5.250% per year. Interest on the Notes will be paid semi-annually in arrears on March 30 and September 30 of each year, be

Calculation of Filing Fee Tables Form S-3 (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule

EX-FILING FEES Exhibit 107 Calculation of Filing Fee Tables Form S-3 (Form Type) NiSource Inc.

NiSource Inc. $750,000,000 5.250% Notes due 2028 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated March 21, 2023) Issuer: NiSource Inc. Security: 5.250% Notes due 2028 (the “Notes”) Ratings (Moody’s; S&P; Fitch)*: Baa2 (stable)/BBB+ (st

Filed Pursuant to Rule 433 Registration Statement (No. 333-268084) March 21, 2023 NiSource Inc. $750,000,000 5.250% Notes due 2028 PRICING TERM SHEET (To Preliminary Prospectus Supplement dated March 21, 2023) Issuer: NiSource Inc. Security: 5.250% Notes due 2028 (the “Notes”) Ratings (Moody’s; S&P; Fitch)*: Baa2 (stable)/BBB+ (stable)/BBB (stable) Size: $750,000,000 Public Offering Price: 99.829%

Subject to Completion, dated March 21, 2023

424B5 Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-268084 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not p

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   )

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.   ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permit

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 14, 2023 NiSource Inc. (Exa

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 14, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number

NiSource announces leadership changes and additions

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE: March 15, 2023 NiSource announces leadership changes and additions MERRILLVILLE, Ind. - NiSource (NYSE: NI) today announced the appointment of Michael Luhrs to the NiSource executive leadership team, along with a reconfiguration of leadership responsibilities for several others on that team. Michael Luhrs is joining NiSource’s executive leadership team o

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 10, 2023 NiSource Inc. (Exa

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 10, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) Commission File Number

Form 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☑ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2022 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Exact name

Exhibit 10.59 to the NiSource Inc. Form 10-K

Exhibit 10.59 NiSource Inc. 2020 Omnibus Incentive Plan 2023 Restricted Stock Unit Award Agreement This Restricted Stock Unit Award Agreement (the “Agreement”), is made and entered into as of [DATE] (the “Grant Date”), by and between NiSource Inc., a Delaware corporation (the “Company”), and [NAME], an Employee of the Company or an Affiliate (the “Grantee”), pursuant to the terms of the NiSource I

NiSource announces 2022 results, raises 2023 guidance

FOR IMMEDIATE RELEASE: February 22, 2023 NiSource announces 2022 results, raises 2023 guidance •2022 diluted NOEPS tops guidance range; 2023 guidance range increased •NIPSCO minority interest sale launched and on track for 2023 MERRILLVILLE, Ind.

Exhibit 10.58 to the NiSource Inc. Form 10-K

Exhibit 10.58 NiSource Inc. 2020 Omnibus Incentive Plan 2023 Performance Share Unit Award Agreement This Performance Share Unit Award Agreement (the “Agreement”) is made and entered into as of [DATE] (the “Grant Date”), by and between NiSource Inc., a Delaware corporation (the “Company”), and [NAME], an Employee of the Company or an Affiliate (the “Grantee”), pursuant to the terms of the NiSource

List of Subsidiaries.

EX-21 6 ni-ex21x20221231.htm EX-21 Exhibit 21 SUBSIDIARIES OF NISOURCE as of December 31, 2022 Segment/Subsidiary GAS DISTRIBUTION OPERATIONS State of Incorporation Bay State Gas Company d/b/a Columbia Gas of Massachusetts Massachusetts Central Kentucky Transmission Company Delaware Columbia Gas of Kentucky, Inc. Kentucky Columbia Gas of Maryland, Inc. Delaware Columbia Gas of Ohio, Inc. Ohio Colu

Exhibit 10.57 to the NiSource Inc. Form 10-K

Exhibit 10.57 NiSource Inc. 2020 Omnibus Incentive Plan 2023 Restricted Stock Unit Award Agreement This Restricted Stock Unit Award Agreement (the “Agreement”), is made and entered into as of [DATE] (the “Grant Date”), by and between NiSource Inc., a Delaware corporation (the “Company”), and [NAME], an Employee of the Company or an Affiliate (the “Grantee”), pursuant to the terms of the NiSource I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 22, 2023 NiSource Inc. (

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 22, 2023 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commissio

Exhibit 10.60 to the NiSource Inc. Form 10-K

Exhibit 10.60 NiSource Inc. 2020 Omnibus Incentive Plan 2023 Performance Share Unit Award Agreement This Performance Share Unit Award Agreement (the “Agreement”) is made and entered into as of [DATE] (the “Grant Date”), by and between NiSource Inc., a Delaware corporation (the “Company”), and [NAME], an Employee of the Company or an Affiliate (the “Grantee”), pursuant to the terms of the NiSource

NI / NiSource Inc. / PRICE T ROWE ASSOCIATES INC /MD/ Passive Investment

SC 13G/A 1 ni13gadec22.txt UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 22) NISOURCE INC (Name of Issuer) COMMON STOCK (Title of Class of Securities) 65473P105 (CUSIP NUMBER) December 31, 2022 (Date of Event which Requires Filing of Statement) Check the appropriate box to designate the Rule pursuant to

NI / NiSource Inc. / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SC 13G/A 1 tv0090-nisourceinc.htm SCHEDULE 13G/A SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 14)* Name of issuer: NiSource Inc. Title of Class of Securities: Common Stock CUSIP Number: 65473P105 Date of Event Which Requires Filing of this Statement: December 30, 2022 Check the appropriate box to designate the rule

NI / NiSource Inc. / STATE STREET CORP Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 AMENDED FILING NISOURCE INC (NAME OF ISSUER) COMMON STOCK (TITLE OF CLASS OF SECURITIES) 65473P105 (CUSIP NUMBER) 12/31/2022 (DATE OF EVENT WHICH REQUIRES FILING OF THIS STATEMENT) CHECK THE APPROPRIATE BOX TO DESIGNATE THE RULE PURSUANT TO WHICH THIS SCHEDULE IS FILED: (X

NI / NiSource Inc. / BlackRock Inc. Passive Investment

SC 13G/A 1 us65473p1057012723.txt us65473p1057012723.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: 14) NISOURCE INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 65473P105 - (CUSIP Number) December 31, 2022 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to d

NI / NiSource Inc. / BlackRock Inc. Passive Investment

SC 13G/A 1 us65473p1057012323.txt us65473p1057012323.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: 14) NISOURCE INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 65473P105 - (CUSIP Number) December 31, 2022 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to d

Exhibit 10.1 of the NiSource Inc. Form 8-K

Exhibit 10.1 Execution Version CREDIT AGREEMENT among NISOURCE INC., as Borrower, THE LENDERS PARTY HERETO, and JPMORGAN CHASE BANK, N.A., as Administrative Agent, PNC CAPITAL MARKETS LLC, as Syndication Agent, and BANK OF AMERICA, N.A. and WELLS FARGO BANK, N.A., as Co-Documentation Agents JPMORGAN CHASE BANK, N.A., PNC CAPITAL MARKETS LLC, BANK OF AMERICA, N.A. and WELLS FARGO SECURITIES, LLC, a

Entry into a Material Definitive Agreement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 20, 2022 NiSource Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission file number

Calculation of Filing Fee Tables S-3, 424(b)(5) (Form Type) NiSource Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forwar

Exhibit 107 Calculation of Filing Fee Tables S-3, 424(b)(5) (Form Type) NiSource Inc.

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 10, 2022 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation) (Commission File Number)

Up to $450,000,030 NiSource Inc. Common Stock

Table of Contents Filed pursuant to Rule 424(b)(5) File No. 333-268084 Prospectus Supplement (To Prospectus dated November 1, 2022) Up to $450,000,030 NiSource Inc. Common Stock We may issue, offer and sell up to an aggregate of $450,000,030 of our common stock from time to time through Barclays Capital Inc. (?Barclays?), J.P. Morgan Securities LLC (?J.P. Morgan?), KeyBanc Capital Markets Inc. (?K

Regulation FD Disclosure

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant To Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 7, 2022 NiSource Inc. (Exact name of registrant as specified in its charter) DE 001-16189 35-2108964 (State or other jurisdiction of incorporation or organization) Commission

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2022 ☐ TRANSITION REPORT PURSUANT

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2022 or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-16189 NiSource Inc. (Ex