NISOURCE INC

This summary highlights information that may be expanded upon elsewhere in this proxy statement (“Proxy Statement”). This summary does not contain all of the information that you should consider, and you should read the entire Proxy Statement before voting. The accompanying proxy is solicited on behalf of the Board of Directors of NiSource Inc. (the “Board”) for the 2024 annual meeting of stockholders (the “Annual Meeting”).

2024 ANNUAL MEETING OF STOCKHOLDERS

This Proxy Statement and the accompanying proxy card are first being sent to stockholders on April 1, 2024.

VOTING MATTERS AND BOARD RECOMMENDATIONS

BOARD OF DIRECTORS NOMINEES

*Chair of Committee

See “Proposal 1 – Election of Directors” for more information on our director nominees.

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GOVERNANCE HIGHLIGHTS

See “Corporate Governance” for more information on our corporate governance practices.

Our Company

NiSource is one of the largest fully regulated utility companies in the United States, serving approximately 3.3 million natural gas customers and 500,000 electric customers across six states through its local Columbia Gas and NIPSCO brands. Based in Merrillville, Indiana, NiSource’s approximately 7,400 employees are focused on safely delivering reliable and affordable energy to our customers and the communities we serve.

Our strategies focus on improving safety and reliability, enhancing customer service, pursuing regulatory and legislative initiatives to increase accessibility for customers currently not on our gas and electric service, ensuring customer affordability and reducing emissions while generating sustainable returns. With our strategies in mind, NiSource is committed to providing safe and reliable energy for our customers, which in turn creates value for our stockholders.

EXECUTIVE COMPENSATION HIGHLIGHTS

We have designed our executive compensation program to meet our business objectives, including attracting and retaining top-level executive talent, using various compensation elements and to align executive pay with the long-term and short-term interests of our shareholders. We received more than 94% shareholder support for our Say-on-Pay vote in 2023. We recognize and reward our executive officers through compensation arrangements that link their pay to the Company’s performance, and we ensure an alignment of interests with our shareholders, by including a significant portion of total compensation consisting of at-risk performance-based compensation.

See “Compensation Discussion and Analysis (CD&A)” and “2023 Executive Compensation” for more information on our executive compensation program.

ECONOMIC, ENVIRONMENTAL AND SOCIAL HIGHLIGHTS

We all share in the outcomes related to the future of energy and we are focused on helping ensure the work we do satisfies the long-term energy needs in a way that balances the economic, social, and environmental interests of all its stakeholders. Guiding principles that shape and inform how we make many of our decisions include, but are not limited to:

We announced a goal of net-zero greenhouse gas emissions by 2040 covering both Scope 1 and Scope 2 emissions (“Net-Zero Goal”). Our Net-Zero Goal builds on greenhouse gas emission reductions achieved to-date and demonstrates that continued execution of our long-term business plan will drive further greenhouse gas emission reductions. We remain on track to achieve previously announced interim greenhouse gas emission reduction targets by reducing fugitive methane emissions from main and service lines by 50 percent from 2005 levels by 2025 and by reducing Scope 1 greenhouse gas emissions from company-wide operations by 90 percent from 2005 levels by 2030. We plan to achieve our Net-Zero Goal primarily through continuation and enhancement of existing programs, such as the retirement

4 | 2024 Proxy Statement of coal-fired electric generation, increased sourcing of renewable energy, methane reductions from priority pipeline replacement, traditional leak detection and repair, and deployment of advanced leak detection and repair. Additionally, we are active in several efforts to accelerate the development and demonstration of lower-carbon energy technologies and resources, such as hydrogen and renewable natural gas, to enable affordable pathways to economy-wide decarbonization.

For more information on environmental and related matters, see our 2023 Annual Report, our 2023 Interim ESG Report, our 2022 Climate Report and the “Sustainability” section of our website atwww.nisource.com.

We are keenly aware that in addition to being a business entity, we are also a social and community enterprise that includes our employees, partners, customers and the communities we serve. For more information about our business and strategy and about corporate responsibility diversity and sustainability efforts, see our 2023 Annual Report, our 2023 Interim ESG Report and the “Sustainability” and “Diversity, Equity and Inclusion” sections of our website atwww.nisource.com.

GENERAL INFORMATION

Stock Symbol: NI

Stock Exchange: NYSE

Registrar and Transfer Agent: Computershare Investor Services

State of Incorporation: Delaware

Corporate Headquarters: 801 E. 86 th Avenue, Merrillville, Indiana 46410

Corporate Website: www.nisource.com

We use the terms “NiSource,” the “Company,” “we,” “our” and “us” in this Proxy Statement to refer to NiSource Inc.