Proxy Statement (Form DEF 14A)

Mission, Strategy and Core Values

Mission - Why we exist

Delivering natural gas for a better tomorrow

Strategy - How we get there

Core Values - Our Compass

April 2, 2025

Dear Shareholder:

You are cordially invited to attend the 2025 Annual Meeting of Shareholders of ONE Gas, Inc. on Thursday, May 22, 2025, at 9:00 a.m. (Central Daylight Time) to be held in a virtual-only meeting format with no physical location. Information on how to attend and participate virtually in the annual meeting is provided under "About the 2025 Annual Meeting" in the accompanying proxy statement. You will not be able to participate in the 2025 Annual Meeting in person.

The matters to be considered and voted on at the meeting are set forth in the accompanying Notice of Annual Meeting of Shareholders and are described in the accompanying proxy statement. A copy of our 2024 annual report to shareholders is also enclosed. A report on our 2024 performance will be presented at the meeting.

Whether or not you participate in the virtual Annual Meeting, it is important that your shares be represented and voted at the meeting. Therefore, proxies are being solicited so that each shareholder has an opportunity to vote by proxy. You can authorize a proxy over the internet or by telephone. Instructions for these convenient services are included in the proxy statement and the proxy card. Of course, if you prefer, you may vote by mail by signing, dating and returning the enclosed proxy card in the enclosed postage-paid envelope.

If your shares are held by a broker, bank or other holder of record, unless you provide them with voting instructions, your shares will not be voted in the election of directors or in certain other important proposals as described in the accompanying proxy statement. Consequently, please provide your voting instructions to your broker, bank or other holder of record in a timely manner to ensure that your shares will be voted. As always, we encourage you to vote your shares prior to the annual meeting.

Regardless of the number of shares you own, your vote is important. I urge you to submit your proxy or voting instructions as soon as possible to ensure your shares will be voted.

Thank you for your investment in ONE Gas and your continued support.

Sincerely,

JOHN W. GIBSON

Chairman of the Board

ONE GAS, INC. NOTICE OF 2025 ANNUAL MEETING OF SHAREHOLDERS

PROXY STATEMENT

This proxy statement describes important issues affecting our company and is furnished in connection with the solicitation of proxies by our Board for use at our 2025 Annual Meeting of Shareholders to be held at the time and place set forth in the accompanying notice.

The abbreviations, acronyms and terms used in this Proxy Statement are defined as follows:

SAFE HARBOR FOR FORWARD-LOOKING STATEMENTS

Any statements in this proxy statement that are not historical information, including statements concerning plans and objectives of management for future operations, economic performance or related assumptions, are forward-looking statements made under the provision of the "Safe Harbor" section of the Private Securities Litigation Reform Act of 1995. Forward-looking statements may include words such as "anticipate," "believe," "continue," "could," "estimate," "expect," "forecast," "goal," "guidance," "intend," "may," "might," "outlook," "plan," "potential," "project," "scheduled," "should," "will," "would" and other words and terms of similar meaning. Although we believe that our expectations regarding future events are based on reasonable assumptions, we can give no assurance that such expectations or assumptions will be achieved. Important factors that could cause actual results to differ materially from those in the forward-looking statements are described under Part I, Item 1A, Risk Factors, and Part II, Item 7, Management's Discussion and Analysis of Financial Condition and Results of Operations and "Forward-Looking Statements," in our 2024 Annual Report on Form 10-K andother filings with the SEC. All forward-looking statements included in this document are based on information available to us on the date hereof. We will not undertake and specifically decline any obligation to update any forward-looking statements, except as required under applicable law.

For more than 100 years, our business has built a legacy of safely delivering reliable and affordable natural gas to our customers. We are committed to a clear mission - to deliver natural gas for a better tomorrow. For more information about our approach to corporate responsibility, visit our website at www.onegas.com, the contents of which are expressly not incorporated herein by this reference.

The Board is responsible for overseeing our corporate sustainability strategy and associated disclosures. We understand that delivering a sustainable energy future requires a sharp focus on ensuring resiliency and reliability and reducing the environmental impact of our delivery systems. As a result, we established an ESG Steering Committee led by our CFO, which included representatives from most functional areas and other senior management team members. The primary purpose of the ESG Steering Committee is to provide vision, leadership, direction and oversight of our sustainability programs, processes and disclosures. We continue to focus on integrating sustainable business practices and providing transparency into our strategy, while creating long-term shareholder value.

Our core values-safety, ethics, inclusion and diversity, service and value-underlie all we do and guide our sustainability strategy, which is reviewed and validated annually as part of our enterprise risk management and strategic planning processes.

SAFETY AND HEALTH

Safety is our number one core value and is the foundation of everything we do. By monitoring the integrity of our assets and promoting the safety and health of our employees, customers and communities, we are investing in the long-term sustainability of our businesses.

Our approximately 3,900 employees drive our safety culture and are committed to a goal of zero fatalities and zero incidents. We continue to refine our training, controls, work procedures and other preventive safety and health programs as we strive for zero harm. The key to reducing safety incidents is to stop an accident before it happens, which is why we continue to enhance our preventive safety programs, such as near-miss reporting, vehicle-safety monitoring, risk assessment and others.

Our COO chairs our Environment, Safety, Health and Compliance ("ESH&C") Steering Committee which includes other management team members and senior operations personnel. The primary purpose of the ESH&C Steering Committee is to provide vision, leadership, direction and oversight of our ESH&C programs, processes and management systems. These efforts relate to protecting our employees, the environment and the communities we serve, as well as systems focused on the safe design and operation of our natural gas distribution system.

2024 Safety and Health Performance

ENVIRONMENTAL PERFORMANCE

We recognize the importance of responsible environmental stewardship in creating long-term value for our stakeholders. We are committed to reducing negative environmental impacts and providing reliable and affordable essential energy sources for our customers. As part of our commitment, we have continued to make progress on emissions reductions through various programs, including pipeline replacement and system integrity projects, end-useenergy conservation programs, and providing compressed natural gas for natural gas-poweredvehicles. Our goal to reduce emissions due to leaks from distribution mains and services is 55% by 2035, from a 2005 baseline, factoring in projected system growth. In addition, we participate in several organizations to identify and implement best practices that advance social responsibility, economic vitality and environmental stewardship. For further information, please see our Sustainability Report, which is available on our website at www.onegas.com.

2024 Environmental Updates and Highlights

COMMUNITY INVESTMENT

We are committed to being active members of the communities where we operate. We invest in the areas where we have operations and where our employees live and work not only because it is the right thing to do-it's smart business. By contributing financially and through company-sponsored volunteer work, we can help build stronger communities and create a better quality of life for our employees, customers and the general public.

We accomplish this in several ways, including grants from the ONE Gas Foundation, corporate sponsorships to nonprofit organizations and community volunteer efforts. Primary philanthropic focus areas are Community Enrichment and Assistance, including public spaces and disaster recovery; Education and Workforce Development; and Community Collaboration, including diversity and economic development. In 2024, we prioritized grant requests that involve natural gas safety partnerships, workforce development and classroom enrichment projects involving Science, Technology, Engineering, the Arts and Mathematics ("STEAM") programs.

2024 Community Investment Updates and Highlights

HUMAN CAPITAL MANAGEMENT

Culture and Employee Engagement

Every ONE Gas employee makes a difference and contributes to our success. We actively recruit and retain a high-performing workforce and create a safe, ethical and inclusive culture where top talent wants to work. Our programs and policies help attract, retain and develop our workforce and support our employees' physical, social, emotional and financial well-being. Our holistic approach inspires employees to make healthy personal and professional lifestyle choices.

2024 Human Capital Updates and Highlights

INCLUSION AND DIVERSITY

Our core values include inclusion and diversity, and we believe in creating equal opportunities to recognize the value and voice of every employee. Fostering an inclusive environment based on respect allows our employees to perform their best work and drives our company's success. Our CEO chairs our Inclusion and Diversity Council, which includes both permanent members and rotating members from various functional areas, backgrounds and experiences. The Council provides governance and guidance for sharing our vision of an inclusive and diverse workforce.

All employees are welcomed to join Employee Resource Groups ("ERGs). These voluntary groups drive engagement and collaboration throughout the organization. In addition to connection and collaboration, ERGs assist in attracting talent to our organization, sharing valuable education on various topics, providing professional development opportunities for members and promoting community involvement. In 2024, 36% of ONE Gas employees participated as a member of at least one ERG.

Our annual employee engagement survey focuses on our company values, including Inclusion and Diversity, using Gallup's Inclusiveness Index.

The Company is committed to providing equal opportunity to all employees and applicants and proactively reviews its policies and programs for compliance with all applicable laws, regulations and executive orders. None of the Company's Inclusion and Diversity efforts include quotas or preferences based upon an individual's membership in a particular constituency, and participation in all Inclusion and Diversity activities is voluntary and open to all employees.

POLITICAL ADVOCACY AND CONTRIBUTIONS

We do not contribute corporate funds to political candidates or political action committees. We also do not contribute corporate funds to so-called501(c)(4) social welfare organizations for lobbying. Employee and director contributions to the ONE Gas PAC support various parties, including other political action committees and candidates seeking federal or state offices that support the energy industry and our business interests. A steering committee comprised of senior management representatives and a contributions committee of employees from across our operating areas and business functions oversee all ONE Gas PAC contributions to political candidates.

VOTING

Only shareholders of record at the close of business on March 24, 2025, are entitled to receive notice of and to vote at the annual meeting. As of that date, 59,929,090 shares of our common stock were outstanding. Each outstanding share entitles the holder to one vote on each matter submitted to a vote of shareholders at the meeting. No other class of our stock is entitled to vote on matters to come before the meeting.

Shareholders of record may vote online or by proxy at the annual meeting. All properly submitted proxies received before the commencement of voting at the annual meeting will be voted in accordance with the voting instructions contained on the proxy. Shares for which signed proxies are properly submitted without voting instructions will be voted:

While we know of no other matters that are likely to be brought before the meeting, in the event any other business properly comes before the meeting, proxies will be voted at the discretion of the persons named in the proxy. The persons named as proxies were designated by our Board.

To vote shares held "in street name" through a bank, broker or other holder of record, a shareholder must provide voting instructions to their bank, broker or other holder of record. Brokerage firms, banks and other holders of record are required to request voting instructions for shares they hold on behalf of their customers and others. We encourage you to provide instructions to your bank, broker, or other record holder on how to vote your shares. If your shares are held "in street name," to be able to vote those shares online at the annual meeting, you must obtain a legal proxy, executed in your favor, from the holder of record of those shares as of the close of business on March 24, 2025.

The rules of the NYSE determine whether proposals presented at shareholder meetings are routine or non-routine.If a proposal is routine, a broker or other entity holding shares for an owner in street name may vote for the proposal without receiving voting instructions from the owner under certain circumstances. If a proposal is non-routine,the broker or other entity may vote on the proposal only if the owner has provided voting instructions. A "broker non-vote"occurs when the broker or other entity is unable to vote on a proposal because the proposal is non-routineand the owner does not provide any voting instructions. Under the rules of the NYSE, Proposals 1 and 3 are considered to be non-routine,and Proposal 2 is considered to be routine. Accordingly, if you do not provide voting instructions to your brokerage firm or other entity holding your shares, your brokerage firm or other entity holding your shares will not be permitted under the rules of the NYSE to vote your shares on Proposals 1 and 3 and will be permitted under the rules of the NYSE to vote your shares on Proposal 2 at its discretion.

Please provide your voting instructions to your broker, bank or other holder of record so that your shares may be voted.

Representatives of our stock transfer agent, Equiniti Trust Company, LLC d/b/a EQ Shareowner Services, will be responsible for tabulating and certifying the votes cast at the annual meeting.

QUORUM

The holders of a majority of the shares entitled to vote at the annual meeting, present online or by proxy, constitute a quorum for the transaction of business at the annual meeting. In determining whether we have a quorum, we count abstentions and broker non-votesas present.

If a quorum is not present at the scheduled time of the meeting, the shareholders who are present online or by proxy may adjouthe meeting until a quorum is present. If the time and place of the adjourned meeting are announced at the time the adjournment is taken, no other notice will be given. However, if the adjournment is for more than 30 days, or if a new record date is set for the adjourned meeting, a notice will be given to each shareholder entitled to receive notice of and to vote at the meeting.

MATTERS TO BE VOTED UPON

At the annual meeting, the following matters will be voted upon:

VOTES REQUIRED

Proposal 1 - Election of Directors.Our bylaws provide for majority voting for directors in uncontested elections. We expect that the election of directors at our 2025 Annual Meeting will be uncontested. Under the majority voting standard, to be elected a nominee must receive a number of "For" votes that exceed 50 percent of the votes cast with respect to that director's election. Abstentions and broker non-votes,if any, do not count as votes cast with respect to the election of directors.

Our corporate governance guidelines require that if an uncontested nominee for director does not receive more "For" than "Against" votes, they must promptly tender their resignation to our Board. The Board (excluding the director who tendered the resignation) will then evaluate the resignation in light of our company's and our shareholders' best interests in determining whether to accept or reject the resignation or whether other action should be taken. The Board will announce publicly its decision regarding any tendered resignation.

Proposal 2 - Ratification of Selection of PricewaterhouseCoopers LLP as our Independent Registered Public Accounting Firm for the Year ending December31, 2025.In accordance with our bylaws, approval of this proposal requires the affirmative vote of a majority of the voting power of the shareholders present online or by proxy and entitled to vote on this proposal at the meeting. Abstentions will have the same effect as votes against this proposal.

Proposal 3 -Advisory Vote on Executive Compensation.In accordance with our bylaws, approval of this proposal requires the affirmative vote of a majority of the voting power of the shareholders present online or by proxy and entitled to vote on this proposal at the meeting. Abstentions will have the same effect as votes against this proposal and broker non-votesdo not count as present and entitled to vote for purposes of determining the outcome of the vote on this proposal. The vote on this proposal is advisory and non-bindingon the company and our Board.

REVOKING A PROXY

Any shareholder may revoke their proxy at any time before it is voted at the meeting by (1) notifying our corporate secretary in writing (the mailing address is Corporate Secretary, ONE Gas, Inc., 15 East Fifth Street, Tulsa, Oklahoma 74103), (2) authorizing a later proxy via the internet or by telephone, (3) returning a later dated proxy card, or (4) voting online at the meeting. A shareholder's presence without voting at the annual meeting will not automatically revoke a previously delivered proxy, and any revocation during the meeting will not affect votes previously taken.

If your shares are held in a brokerage account or by a bank or other holder of record, you may revoke any voting instructions you may have previously provided in accordance with the revocation instructions provided by the broker, bank or other holder of record.

PROXY SOLICITATION

Solicitation of proxies will be primarily by mail and telephone. We have engaged Morrow Sodali LLC, 333 Ludlow Street, 5^th Floor, South Tower, Stamford, CT 06902, to solicit proxies for a fee of $11,000 plus out-of-pocketexpenses. In addition, certain of our officers, directors and employees may solicit proxies on our behalf in person or by mail, telephone, fax or email, for which such persons will receive no additional compensation. We will pay all costs of soliciting proxies. We will also reimburse brokerage firms, banks and other custodians, nominees and fiduciaries for their reasonable expenses for forwarding proxy materials to our shareholders.

Our Board and management are committed to maintaining strong corporate governance practices that allocate rights and responsibilities among our Board, management and our shareholders in a manner that benefits the long-term interests of our shareholders. Our corporate governance practices are designed to satisfy regulatory and stock exchange requirements and provide for effective oversight and management of our company.

Our Corporate Governance Committee regularly reviews our corporate governance practices, including comparing our practices with those recommended by various corporate governance authorities, the expectations of our shareholders and the practices of other leading public companies. Our Corporate Governance Committee also regularly reviews our corporate governance practices in light of proposed and adopted laws and regulations, including the SEC rules and the NYSE's rules and listing standards.

CORPORATE GOVERNANCE GUIDELINES

Our Board has adopted corporate governance guidelines that address key areas of our corporate governance, including director qualification standards, including the requirement that a majority of our directors be "independent" under the applicable independence requirements of the NYSE; director responsibilities; director access to management; director compensation; management succession; evaluation of the performance of our Board; ESG oversight; and the structure and operation of our Board. Our Board periodically reviews our corporate governance guidelines and may revise the guidelines from time to time as conditions warrant. The full text of our corporate governance guidelines is published on and may be printed from our website at www.onegas.comand is also available from our corporate secretary upon request.

CODE OF BUSINESS CONDUCT AND ETHICS

Our Board has adopted a code of business conduct and ethics that applies to our directors, officers (including our principal executive and financial officers, controller and other persons performing similar functions) and all other employees. We require all directors, officers and employees to adhere to our code of business conduct and ethics in addressing the legal and ethical issues encountered in conducting their work for our company. Our code of business conduct and ethics requires that our directors, officers and employees avoid conflicts of interest, comply with all applicable laws and other legal requirements, conduct business in an honest and ethical manner and otherwise act with integrity and in our company's best interests. All directors, officers and employees are required to report any conduct that they believe to be an actual or apparent violation of our code of business conduct and ethics.

The full text of our code of business conduct and ethics is published and may be printed from our website at www.onegas.com. It is also available from our corporate secretary upon request. We intend to disclose on our website any future amendments to, or waivers of, our code of business conduct and ethics, as required by the rules of the SEC and the NYSE.

DIRECTOR INDEPENDENCE

Our corporate governance guidelines provide that a majority of our Board will be "independent" under the applicable independence requirements of the NYSE. These guidelines and the rules of the NYSE provide that, in qualifying a director as "independent," the Board must make an affirmative determination that the director has no material relationship with our company, either directly or as a partner, shareholder or officer of an organization that has a relationship with our company. In making this determination with respect to each director serving on the Executive Compensation Committee, under the rules of the NYSE, the Board is required to consider all factors specifically relevant to determine whether the director has a relationship to our company that is material to that director's ability to be independent of management in connection with the duties of a member of that committee.

Our Board has also adopted director independence guidelines that specify the types of relationships the Board has determined to be categorically immaterial. Directors who meet these standards are considered to be "independent." The full text of our director independence guidelines is published and may be printed from our website at www.onegas.com. It is also available from our corporate secretary upon request.

Our Board has determined affirmatively that members Tracy E. Hart, Deborah A. P. Hersman, Michael G. Hutchinson, Sanjay D. Meshri, Pattye L. Moore, Eduardo A. Rodriguez and Yves C. Siegel have no material relationship with our company, and each qualifies as "independent" under our corporate governance guidelines, our director independence guidelines and the rules of the NYSE. Our Board has also determined that Robert E. Evans and Douglas H. Yaeger, each of whom retired from the Board immediately prior to the 2024 annual meeting, qualified as independent during the time they served on the Board in 2024. The Board recognizes that John W. Gibson is independent under our corporate governance guidelines, our director independence guidelines and the rules of the NYSE. However, due to the US proxy voting guidelines of Institutional Shareholder Services that provide that a former CEO is always considered non-independent,and Mr. Gibson served as the initial CEO of the Company, the Board has determined that Mr. Gibson is not independent. In determining whether certain of our directors qualify as "independent" under our director independence guidelines, our Board considered the receipt by certain directors or their immediate family members (or entities of which they are members, directors, partners, executive officers, or counsel) of natural gas service from us at regulated rates on terms generally

In addition, the lead independent director has the authority to call meetings of the independent directors and, if requested by major shareholders, will be reasonably available for consultation and direct communication with such shareholders. The Lead Independent Director may also perform duties otherwise assigned to the Chairman of the Board when the offices of the Chairman of the Board and the CEO are combined.

SUCCESSION PLANNING

A key responsibility of the CEO and the Board is ensuring that an effective process is in place to provide continuity of leadership over the long term at all levels in our company. Each year, succession-planning reviews are held at every significant organizational level of the company, culminating in a full review of senior leadership talent by our independent directors. During this review, the CEO, the Chairman of the Board and the independent directors discuss future candidates for senior leadership positions, including all NEOs, succession timing for those positions and development plans for the highest-potential candidates. This process ensures continuity of leadership over the long term, and it forms the basis on which our company makes ongoing leadership assignments. It is a key success factor in managing the long-term planning and investment lead times of our business.

In addition, we have a written CEO emergency succession plan pursuant to which the CEO maintains in place at all times and reviews with the non-managementdirectors, a confidential plan for the timely and efficient transfer of responsibilities in the event of an emergency or sudden incapacitation or departure of the CEO.

OUR BOARD AND CORPORATE STRATEGY

Our Board is actively involved in overseeing, reviewing and guiding our corporate strategy. Our Board formally reviews our company's business strategy, including the risks and opportunities facing our company and its business, at an annual strategic planning session. Our Board regularly discusses corporate strategy throughout the year with management formally, informally, and during executive sessions of the Board as appropriate. As discussed in "Risk Oversight" below, our Board views risk management and oversight as integral to our strategic planning process, including mapping key risks to our corporate strategy and seeking to manage and mitigate risk. Our Board also views its composition as a critical component of effective strategic oversight. Accordingly, our Board and relevant Board committees consider our business strategy and the company's regulatory, geographic and market environments when assessing board composition, director succession, executive compensation and other matters of importance.

SHAREHOLDER ENGAGEMENT

Our Board believes that accountability to shareholders is a mark of good corporate governance and that regular shareholder engagement is important to our company's success. Our company frequently engages with shareholders on a variety of topics, with a particular focus on matters relating to our company's publicly disclosed strategy and financial performance. Our company also engages with shareholders to discuss matters relating to ESG, compensation and other current and emerging issues that the Board and our management understand are important to our shareholders. In addition to this direct engagement, our company also maintains a number of complementary mechanisms that allow our shareholders to effectively communicate to our Board and management, including:  

RISK OVERSIGHT

We have integrated a comprehensive Enterprise Risk Management ("ERM") framework as part of strategy setting and driving performance throughout the company, which includes identifying, aggregating, monitoring, measuring, assessing and managing risks that could affect our ability to fulfill our business objectives or execute our corporate strategy. These risks generally relate to strategic, operational, financial, regulatory compliance and human resources issues. Our CFO oversees our ERM approach. It is designed to enable our Board to establish a mutual understanding with management of the effectiveness of our risk-management practices and capabilities, to review our risk exposure and to elevate certain key risks for discussion at the Board level. Management and our Board believe that risk management is an integral part of our annual strategic planning process, which addresses, among other things, the risks and opportunities facing our company.

Not all risks can be dealt with in the same way. Some risks may be easily perceived and controllable, and other risks are unknown; some risks can be avoided or mitigated by particular behavior, and some risks are unavoidable as a practical matter. For some risks, the potential adverse impact would be minor and, as a matter of business judgment, it may not be appropriate to allocate significant resources to avoid the adverse impact. In other cases, the adverse impact could be significant, and it is prudent to expend resources to seek to avoid or mitigate the potential adverse impact. Management is responsible for identifying risks and controls related to our significant business activities; mapping the risks to our corporate strategy; and developing programs and recommendations to determine the sufficiency of risk identification, the balance of potential risk to potential reward and the appropriate manner in which to control and mitigate risk. Much of this work is led by our ESH&C Steering Committee, which is chaired by our COO, and includes other members of the management team and senior operations personnel. The ESH&C Steering Committee's primary purpose is to provide vision, leadership, direction, and oversight of our ESH&C programs, processes, and management systems for the protection of the employees, the environment, and the communities we serve, as well as the processes and procedures focused on the safe design and operation of our system.

The Board implements its risk oversight responsibilities by having management provide periodic briefings and informational sessions on the risks and uncertainties our company faces and how it seeks to control and mitigate those risks. In some cases, as with risks associated with ESG, risk oversight is addressed as part of the full Board's engagement with the CEO and management. ESG risks are also evaluated at the management level through our ESG Steering Committee. The ESG Steering Committee is chaired by our CFO, and includes other members of the management team and senior management personnel. The ESG Steering Committee is charged with providing oversight and guidance to the company on emerging ESG issues and considering how to implement ESG matters consistent with our overall strategy. The ESG Steering Committee also provides oversight of the entire ERM process.

The Board annually reviews a management assessment of our company's various operational and regulatory risks, their relative magnitude, and management's plan for mitigating these risks. The Board also reviews risks related to our company's business strategy at its annual strategic planning meeting and at other meetings as appropriate.

Recognizing that cybersecurity risk is one of the significant risks to our business, the Board has retained responsibility for overseeing policies and procedures related to cybersecurity and data privacy matters. The Board routinely evaluates our cybersecurity strategy to review its effectiveness. The Board receives updates from management regarding cybersecurity and other information and operations technology risks.

In certain cases, a Board committee is responsible for oversight of specific risk topics. For example, the Audit Committee oversees risk issues associated with our overall financial reporting and disclosure process and legal compliance, as well as reviewing policies and procedures on risk-control assessment and accounting risk exposure, including our companywide risk control activities. Our general counsel provides compliance and ethics reports to the Audit Committee at every regular committee meeting. The Audit Committee meets with our executive officers and meets with our Director-Audit Services, as well as with our independent registered public accounting firm, in separate executive sessions at each of its in-person/virtualmeetings during the year, at which time risk issues are discussed regularly.

In addition, our Executive Compensation Committee oversees risks related to our compensation program, as discussed in greater detail elsewhere in this proxy statement, and our Corporate Governance Committee oversees risks related to our governance practices and policies.

BOARD AND COMMITTEE MEMBERSHIP

Our business, property and affairs are managed under the direction of our Board. Members of our Board are kept informed of our business through discussions with our CEO and other officers, by reviewing materials provided to them periodically and in connection with Board and committee meetings, by visiting our offices and by participating in meetings of the Board and its committees.

During 2024, the Board held nine regular meetings (six in-personand three telephonic meetings) and one special telephonic meeting. All of our incumbent directors who served on the Board during 2024 attended all of the meetings of the Board and Board committees on which they served.

Our corporate governance guidelines provide that members of our Board are expected to attend our Annual Meeting of Shareholders. Based on the nature of the convening method of the Annual Meeting of Shareholders, members of our Board may attend the meeting in person or by conference telephone or videoconference software. All then-current members of the Board attended the 2024 Annual Meeting of Shareholders.

The Board has three standing committees: the Audit Committee, the Executive Compensation Committee and the Corporate Governance Committee. The table below provides the current membership of our Board and each of our Board committees. Our Board has determined affirmatively that each member of our Audit Committee, Executive Compensation Committee and Corporate Governance Committee is "independent" under our corporate governance guidelines, our director independence guidelines and the rules of the NYSE.

Our Board has adopted written charters for each of its Audit, Executive Compensation and Corporate Governance Committees. Copies of the charters of each of these committees are available on and may be printed from our website at www.onegas.com.Copies are also available from our corporate secretary upon request. The responsibilities of our Board committees are summarized below. From time to time, the Board, at its discretion, may form other committees.

DIRECTOR NOMINATIONS

Our corporate governance guidelines provide that the Board is responsible for nominating candidates for Board membership and for delegating the screening process to the Corporate Governance Committee of the Board. This committee, with recommendations and input from our Chairman of the Board, CEO and the directors, evaluates the qualifications of each director candidate and assesses the appropriate mix of skills, qualifications and characteristics required of Board members in the context of the perceived needs of the Board at a given point in time. The Corporate Governance Committee is responsible for recommending to the full Board candidates for nomination by the Board for election as members of our Board.

Our corporate governance guidelines provide that candidates for nomination by the Board must be committed to devote the time and effort necessary to be productive members of the Board and that, in selecting directors, the Board seeks to maintain a mix of skills that includes, but is not limited to, the following areas of core competency: accounting and finance; investment banking; business judgment; management; industry knowledge; crisis response; international business; leadership; applicable ESG matters; strategic vision; law; and corporate relations. In addition, the Board and Corporate Governance Committee maintain a diverse pool for potential Board positions considering professional and personal background, gender, sex, sexual orientation, gender identity or expression, race, ethnicity, age and nationality.

The Corporate Governance Committee's charter provides that it has the responsibility, in consultation with the Chairman of the Board and CEO, to search for, recruit, screen, interview and recommend to the Board candidates for the position of director as necessary to fill vacancies on the Board or the additional needs of the Board and to consider management and shareholder recommendations for candidates for nomination by the Board. In carrying out this responsibility, the Corporate Governance Committee evaluates the qualifications and performance of incumbent directors and determines whether to recommend them for re-electionto the Board. In addition, this committee determines, as necessary, the portfolio of skills, experience, diversity, perspective and background required for the effective functioning of the Board considering our business strategy and our regulatory, geographic and market environments.

Our corporate governance guidelines contain a policy regarding the Corporate Governance Committee's consideration of prospective director candidates recommended by shareholders for nomination by our Board. Under this policy, and in accordance with our bylaws, any shareholder who wishes to recommend a prospective candidate for nomination by our Board for election at our 2026 annual meeting should send a letter of recommendation to our corporate secretary at our principal executive offices by no later than December 3, 2025. The letter should include the name, address and number of shares owned by the recommending shareholder (including, if the recommending shareholder is not a shareholder

of record, proof of ownership of the type referred to in Rule 14a-8(b)(2)of the proxy rules of the SEC), the prospective candidate's name and address, a description of the prospective candidate's background, qualifications and relationships, if any, with our company and all other information requested by our Board for determining whether the prospective candidate meets the independence standards under the rules of the NYSE and our director independence guidelines. A signed statement from the prospective candidate should accompany the letter of recommendation indicating that they consent to be considered as a nominee of the Board and that, if nominated by the Board and elected by the shareholders, they will serve as a director. The Corporate Governance Committee will evaluate prospective candidates recommended by shareholders for nomination by our Board in light of the various factors set forth above.

Neither the Corporate Governance Committee, the Board, nor our company itself discriminates in any way against prospective candidates for nomination by the Board on the basis of age (subject to the mandatory retirement age set forth in the company's bylaws), sex, sexual orientation, gender identity or expression, race, ethnicity, national origin, religion, or other personal characteristics. There are no differences in the manner in which the Corporate Governance Committee or the Board evaluates prospective candidates based on whether the prospective candidate is recommended by a shareholder or by the Corporate Governance Committee, provided that the recommending shareholder furnishes to our company a letter of recommendation containing the information described above along with the signed statement of the prospective candidate referred to above.

In addition to having the ability to recommend prospective candidates for nomination by our Board, under our bylaws, shareholders may themselves nominate candidates for election at an annual meeting of shareholders. Any shareholder who desires to nominate candidates for election as directors at our 2026 annual meeting must follow the procedures set forth in our bylaws. Under these procedures, a notice of a shareholder nomination for the election of a director must be received by our corporate secretary at our principal executive offices not less than 120 calendar days before the first anniversary of the date that our proxy statement was released to shareholders in connection with our 2025 Annual Meeting of Shareholders (i.e., notice must be received no later than December 3, 2025). If the date of the 2026 annual meeting is more than 30 days from the first-anniversary date of the 2025 meeting, our corporate secretary must receive notice of a shareholder nomination by the close of business on the tenth day following the earlier of (i) the day on which notice of the date of the meeting is mailed to shareholders or (ii) the day on which public announcement of the meeting date is made. In accordance with our bylaws, a shareholder notice must contain certain information about the candidate the shareholder desires to nominate for election as a director, including: (a) the name, age, business address and residence address of such person; (b) the principal occupation or employment of such person; (c) the class or series and number of our shares that are owned beneficially or of record by such person and any affiliates or associates of such person; (d) the name of each nominee holder of our shares owned beneficially but not of record by such person or any affiliates or associates of such person, and the number of our shares held by each such nominee holder; (e) whether and the extent to which any derivative instrument, swap, option, warrant, short interest, hedge or profit interest or other transaction has been entered into by or on behalf of such person, or any affiliates or associates of such person, with respect to our shares; (f) whether and the extent to which any other transaction, agreement, arrangement or understanding (including any short position or any borrowing or lending of our shares) has been made by or on behalf of such person, or any affiliates or associates of such person, the effect or intent of any of the foregoing being to mitigate loss to, or to manage risk or benefit of stock price changes for, such person, or any affiliates or associates of such person, or to increase or decrease the voting power or pecuniary or economic interest of such person, or any affiliates or associates of such person, with respect to our shares; (g) such person's written and executed representation and agreement (in the form provided by the corporate secretary upon written request) that such person (1) is not and will not become a party to any agreement, arrangement or understanding with, and has not given any commitment or assurance to, any person or entity as to how such person, if elected as a director of the company, will act or vote on any issue or question, (2) is not and will not become a party to any agreement, arrangement or understanding with any person or entity other than the company with respect to any direct or indirect compensation, reimbursement or indemnification in connection with service or action as a director of the company that has not been disclosed to the company in such representation and agreement and (3) in such person's individual capacity, would be in compliance, if elected as a director of the company, and, if elected as a director, will comply with, all applicable publicly disclosed confidentiality, corporate governance, conflict of interest, Regulation FD, code of conduct and ethics, and stock ownership and trading policies and guidelines of the company; (h) such person's completed written questionnaire with respect to the background and qualification of such individual and the background of any other person or entity on whose behalf, directly or indirectly, the nomination is being made (which form of questionnaire shall be promptly provided by the corporate secretary to the requesting shareholder upon written request) and (i) all other information relating to such person that would be required to be disclosed in connection with a solicitation of proxies for the election of such person as a director, or would be otherwise required to be disclosed in connection with such solicitation, in each case pursuant to Rule 14a-19under the Exchange Act, (including without limitation such person's written consent to being named in the proxy statement as a nominee and to serving as a director if elected).

In addition, as to the shareholder giving the notice and the beneficial owner, if any, on whose behalf the nomination is made, the notice must set forth: (a) the name and address, as they appear on the company's books, of such shareholder, and the name and address of such beneficial owner, if any, and any other shareholders known by such shareholder to be supporting such nominee(s); (b) the class and number of our shares that are owned beneficially and of record by such person and any affiliates or associates of such person; (c) the name of each nominee holder of our shares owned beneficially but not of record by such person or any affiliates or associates of such person, and the number of such shares held by each such nominee holder; (d) whether and the extent to which any derivative instrument, swap, option, warrant, short interest, hedge or profit interest or other transaction has been entered into by or on behalf of such person, or any affiliates or associates of such person, with respect to

our shares; (e) whether and the extent to which any other transaction, agreement, arrangement or understanding (including any short position or any borrowing or lending of our shares) has been made by or on behalf of such person, or any affiliates or associates of such person, the effect or intent of any of the foregoing being to mitigate loss to, or to manage risk or benefit of stock price changes for, such person, or any affiliates or associates of such person, or to increase or decrease the voting power or pecuniary or economic interest of such person, or any affiliates or associates of such person, with respect to our shares; (f) a representation that the shareholder giving notice intends to appear online or by proxy at the annual meeting or special meeting to nominate the persons named in its notice; (g) a description of all agreements, arrangements and understandings between such person or any affiliate or associate of such person, and any other person or persons (including their names) in connection with the nomination by such shareholder; and (h) all other information that would be required to be disclosed by such person as a participant in a solicitation of proxies for the election of directors in a contested election, or would be otherwise required to be disclosed in connection with such solicitation, in each case pursuant to Section 14 under the Exchange Act (including all other information required by Rule 14a-19under the Exchange Act). This information must be updated and supplemented by such shareholder and beneficial owner, if any, (i) so that the information provided or required to be provided in such notice shall be true and correct as of the record date for determining the shareholders entitled to receive notice of and to vote at such annual meeting or special meeting and (ii) to provide evidence that the shareholder providing notice of any nomination has solicited proxies from holders representing at least sixty-seven percent (67%) of the voting power of the shares entitled to vote in the election of directors, and any such update and supplement shall be delivered to or be mailed to and received by the corporate secretary at the principal executive offices no later than five (5) business days after the shareholder files a definitive proxy statement in connection with the meeting.

At the request of the company, each proposed nominee must submit to the corporate secretary such other information as the company may reasonably require, including such information as may be necessary or appropriate in determining the eligibility of such proposed nominee to serve as an independent director of the company or that could be material to a reasonable shareholder's understanding of the independence, or lack thereof, of such nominee.

DIRECTOR COMPENSATION

The Executive Compensation Committee's independent compensation consultant, Meridian, annually advises the Committee on matters related to non-managementdirector compensation, including competitive market data for the company's peer group. The Committee reviews and discusses the director compensation information provided by Meridian and makes a recommendation to the full Board with respect to non-managementdirector compensation. The Committee's philosophy with respect to non-managementdirector compensation is to target at or below the market median. The components of non-managementdirector compensation include an annual cash retainer, additional annual cash retainers for the Chairman of the Board, the Lead Independent Director, the chairs of the Audit, Executive Compensation and Corporate Governance Committees and an annual stock retainer. No separate per-meetingfees are paid to the non-managementdirectors.

Compensation for each of our non-managementdirectors for their service on our Board is paid on an annual meeting date basis. Based on the market information provided by Meridian in November 2023 and February 2024, compensation remained unchanged for the period of May 23, 2024, through May 21, 2025. Director compensation was last increased in 2022 to address market shortfalls in the stock retainer, Audit Committee chair and Lead Independent Director retainers as identified by Meridian.

All directors are reimbursed for reasonable expenses incurred in connection with attendance at Board and committee meetings.

The CEO, as the sole management director, receives no compensation for his service as a director.

Our Board has established minimum share ownership guidelines for members of our Board. The guidelines provide that within five years after joining the Board, each non-managementdirector will own shares of the company's common stock having a value, at a minimum, of five times the annual cash retainer for service on the Board (excluding annual retainers for service as a chair of a Board committee or for service as Chairman of the Board or as the lead independent director) as established from time to time by the Board. Shares that count toward this ownership guideline include shares owned outright in the director's name, shares held in trust for the director's benefit or the benefit of the director's immediate family, and phantom shares held in the director's account under any company deferred compensation plan for non-employeedirectors or any similar plan or arrangement. A non-managementdirector will not be allowed to sell shares of the company's common stock (using established pre-clearanceprocedures) unless such director's holdings of the company's common stock meet the established minimum ownership guideline. All of our non-managementdirectors have satisfied the minimum share ownership guidelines, other than Deborah A. P. Hersman, Sanjay D. Meshri and Yves C. Siegel. Ms. Hersman has until 2028, to satisfy the minimum share ownership guidelines. Messrs. Meshri and Siegel have until 2029 to satisfy the minimum share ownership guidelines.

The following table sets forth the compensation paid to our non-managementdirectors in 2024:

Director Compensation for 2024

COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION

During 2024, Mesdames Hart, Hersman and Moore and Messrs. Hutchinson, Meshri, Rodriguez and Siegel served on our Executive Compensation Committee. Other members who served during 2024 were Robert B. Evans and Douglas H. Yaeger, each of whom retired from the Board immediately prior to the 2024 annual meeting. No member of the Executive Compensation Committee was an officer or employee of the company or its subsidiary during 2024, and no member of this committee was formerly an officer of the company or its subsidiary. In addition, during 2024, none of our executive officers served as a member of a compensation committee or Board of any other entity of which any member of our Board was an executive officer.

Mr. Rodriguez currently serves as Chair of the ONEOK Executive Compensation Committee.

EXECUTIVE SESSIONS OF THE BOARD

The non-managementmembers of our Board meet in regularly scheduled executive sessions without any members of management present. Our Chairman of the Board presides during the non-managementexecutive sessions of the Board. During 2024, the non-managementmembers of our Board met in executive session during each regularly scheduled in-personmeeting of the Board held during the year. We intend to continue this practice of regularly scheduled meetings of the non-managementmembers of our Board.

Our corporate governance guidelines provide that our lead independent director, who is the chair of our Corporate Governance Committee, presides as the chair at executive session meetings of the independent members of our Board. The independent members of the Board meet in regularly scheduled executive sessions without any members of management or non-independentdirectors present in connection with each regularly scheduled in-personmeeting of the Board. During 2024, the independent members of our Board met in executive session during each regularly scheduled in-personmeeting of the Board held during the year. We intend to continue this practice of regularly scheduled meetings of the independent members of our Board.

COMMUNICATIONS WITH DIRECTORS

Generally, our Board believes that it is management's role to speak for our company. Directors refer all inquiries regarding our company from institutional investors, analysts, the news media, customers or suppliers to our CEO or his designee. Our Board also believes that any communications between members of the Board and interested parties, including shareholders, should be conducted with the knowledge of our CEO. Interested parties, including shareholders, may contact one or more members of our Board, including non-managementdirectors and non-managementdirectors as a group, by writing to the director or directors in the care of our corporate secretary at our principal executive offices. A communication received from an interested party or shareholder will be forwarded promptly to the director or directors to whom the communication is addressed. A copy of the communication also will be provided to our CEO. We will not, however, forward sales or marketing materials and materials that are abusive, threatening or otherwise inappropriate, or correspondence not clearly identified as an interested party or shareholder correspondence.

COMPLAINT PROCEDURES

Our Board has adopted procedures for the receipt, retention and treatment of complaints regarding accounting, internal accounting controls, or auditing matters and complaints or concerns under our code of business conduct and ethics. These procedures allow for the confidential and anonymous submission by employees of concerns regarding questionable accounting or auditing matters and matters arising under our code of business conduct and ethics. The full text of these procedures, known as our whistleblower policy, is published on and may be printed from our website at www.onegas.comand is also available from our corporate secretary upon request.

ELECTION BY MAJORITY VOTE

Our amended and restated certificate of incorporation provides for the annual election of directors. Our Board of Directors currently consists of nine members, each of whose terms will expire at the 2025 annual meeting. Accordingly, the current nine members of our Board of Directors named in this proxy statement will stand for election at the annual meeting.

The Board believes that its current membership reflects a balanced Board with deep experience and diverse expertise.

Our bylaws provide that, in the case of uncontested elections (i.e., elections where the number of nominees is the same as the number of directors to be elected), director nominees are elected by the vote of a majority of the votes cast with respect to that nominee. Abstentions and broker non-voteswith respect to the election of a director do not count as votes cast. Our corporate governance guidelines provide that any uncontested nominee for director who fails to receive the requisite majority vote at an annual or special meeting held for the purpose of electing directors where the election is uncontested must, promptly following certification of the shareholder vote, tender their resignation to the Board. The Board (excluding the director who tendered the resignation) will evaluate any such resignation in light of the best interests of the company and our shareholders in determining whether to accept or reject the resignation or whether other action should be taken. In reaching its decision, the Board may consider any factors it deems relevant, including the director's qualifications, the director's past and expected future contributions to the company, the overall composition of the Board and whether accepting the tendered resignation would cause the company to fail to comply with any applicable rule or regulation (including the NYSE listing requirements and the federal securities laws). The Board will act on the tendered resignation and publicly disclose its decision and rationale within 90 days following certification of the shareholder vote.

The persons named in the accompanying proxy card intend to vote such proxy in favor of the election of each of the nominees named below, who are all current directors unless the proxy provides for a vote against the director. Although the Board has no reason to believe that the nominees will be unable to serve as directors, if a nominee withdraws or otherwise becomes unavailable to serve, the persons named as proxies will vote for any substitute nominee designated by the Board unless contrary instructions are given on the proxy. Except for these nominees, no other person has been recommended to our Board as a potential nominee or otherwise nominated for election as a director.

BOARD REFRESHMENT

During the past year, our Board's refreshment efforts have focused primarily on the composition of our Board, the individual skill sets of current members and additional skills that could be beneficial for the Board and its committees in light of the retirement of Messrs. Evans and Yaeger on May 22, 2024, under our director retirement policy, our commitment to Board diversity and the Board's oversight responsibilities to effectively represent the best interests of our shareholders.

As part of the Board refreshment process, our Board has focused on balancing the diversity of existing directors with new skills and perspectives for an orderly transition of roles and responsibilities on the Board and its committees.

Sanjay D. Meshri and Yves C. Siegel were appointed to the Board, the Audit Committee, the Executive Compensation Committee and the Corporate Governance Committee in July 2024. Mr. Meshri brings to the Board extensive experience in strategic leadership, having operated Advance Research Chemicals, Inc. for over 29 years. Mr. Siegel brings to the Board extensive financial expertise gained from over 30 years of investment advisor experience and is considered a thought leader in the energy sector.

With the addition of Messrs. Meshri and Siegel, our Board believes that its current membership reflects a balanced Board with deep experience and diverse expertise.

DIRECTOR ORIENTATION

Our corporate governance guidelines provide that all new non-managementdirectors will attend a director orientation program offered by the company. The company's director orientation program is individualized for each new director taking into account their prior experience, prior public board service and background. The director orientation program includes one-on-onemeetings with each member of senior management and focuses on introducing new directors to the company.

BOARD COMMITMENTS

Our corporate governance guidelines provide that no non-managementdirector may serve on the board of more than three other public company boards (in addition to serving on the company's Board). A management director may not serve on the board of more than one other public company board (in addition to serving on the company's Board). Service as a director is a significant commitment in terms of both time and responsibility. Accordingly, each director is encouraged to be mindful of their other existing and planned future commitments, so that such other directorships and commitments do not materially interfere with such director's service as an effective and active member of the Board.

The Corporate Governance Committee reviews directorships of all Board members on a regular basis.

BOARD QUALIFICATIONS

Our corporate governance guidelines provide that our Corporate Governance Committee will evaluate the qualifications of each director candidate and assess the appropriate mix of skills and characteristics required of Board members in the context of the perceived needs of the Board at a given point in time. Each director also is expected to:

Our corporate governance guidelines provide that, in nominating candidates and selecting directors to fill vacancies, the Board will seek to maintain a mix of skills that includes, but is not limited to, the following areas of core competency: accounting and finance; investment banking; business judgment; management; industry knowledge; crisis response; international business; leadership; applicable ESG matters; strategic vision; law; and corporate relations. In addition, the Board and Corporate Governance Committee maintain a diverse pool of candidates for potential Board positions considering professional and personal background, gender, sex, sexual orientation, gender identity or expression, race, ethnicity, age and nationality. The Corporate Governance Committee considers diversity in connection with each director nominee, as well as on a periodic basis in connection with the composition of the Board as a whole.

BOARD DIVERSITY

Our Board recognizes the importance of diversity on the Board. Diversity brings different perspectives to Board discussions and deliberations, which contribute to more effective decision making.

Our Board has a broad range of backgrounds, experiences, perspectives and skills. We believe this diversity contributes to the Board's effectiveness in overseeing risk and execution of the company's strategic plan.

We believe our director nominees bring a strong diversity of attributes and experiences to the Board as leaders in business, as shown in the chart below.

Certain information with respect to the nine nominees for election at the annual meeting, is set forth below. This information includes their names, ages, a brief description of their recent business experience, including present occupations and employment, certain directorships that each person holds and the year in which each person became a director of the company. All nine director nominees currently serve as directors of the company.

None of the director nominees are being proposed for election pursuant to any agreement or understanding between the nominees and the company or any other person(s).

There are no family relationships between or among any of the director nominees and executive officers.

DIRECTOR NOMINEES

Set forth below is certain information with respect to each nominee for election as a director, each of whom is a current director. In light of the experience, skills and qualifications of each of the nominees for election as a director as detailed below, our Board has concluded that each nominee should continue as a member of our Board.

RATIFICATION OF THE SELECTION OF PRICEWATERHOUSECOOPERS LLP AS OUR INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM FOR 2025

The Audit Committee has the sole authority and responsibility to evaluate, hire and, where appropriate, replace the company's independent auditor and, in its capacity as a committee of our Board of Directors, is directly responsible for the appointment, compensation and general oversight of the work of the independent auditor. The Audit Committee is also responsible for approving the audit and permissible non-auditservices provided by the independent auditor and the associated fees.

The Audit Committee evaluates the performance of our independent auditor, including the senior audit engagement team, each year and determines whether to re-engagethe current independent auditor or consider other audit firms. In doing so, the Audit Committee considers the quality and efficiency of the services provided by the auditors, the auditors' capabilities, the auditors' technical expertise and knowledge of our operations and industry and the potential impact on the company from changing auditors. In connection with the mandated rotation of the independent auditor's lead engagement partner, the Audit Committee and its Chair are directly involved in the selection of the new lead engagement partner.

Based on this evaluation, the Audit Committee has appointed PricewaterhouseCoopers LLP to serve as our independent auditor for the fiscal year ending December 31, 2025. PricewaterhouseCoopers LLP has served as our independent auditor for 10 years and is considered by management to be well qualified. Further, the Audit Committee and the Board of Directors believe that the continued retention of PricewaterhouseCoopers LLP to serve as our independent auditor is in the best interests of the company and its shareholders.

Our Board has ratified the selection by our Audit Committee of PricewaterhouseCoopers LLP to serve as our independent (consistent with SEC and NYSE policies regarding independence) registered public accounting firm for 2025. In carrying out its duties in connection with the 2024 audit, PricewaterhouseCoopers LLP had unrestricted access to our Audit Committee to discuss audit findings and other financial matters. Representatives of PricewaterhouseCoopers LLP will be present at the annual meeting to answer appropriate questions. They also will have the opportunity to make a statement if they desire to do so.

Approval of this proposal to ratify the selection of PricewaterhouseCoopers LLP as our independent registered public accounting firm requires the affirmative vote of a majority of the voting power of the shareholders present online or by proxy and entitled to vote on this proposal at the meeting. Abstentions will have the effect of a vote against the proposal.

AUDIT AND NON-AUDITFEES

Audit services provided by PricewaterhouseCoopers LLP during the 2024 fiscal year included an integrated audit of our consolidated financial statements and internal control over financial reporting, review of our unaudited quarterly financial statements, consents for and review of documents filed with the SEC, and performance of certain agreed-upon procedures.

The following table presents fees billed for services rendered by PricewaterhouseCoopers LLP for the years ended December 31, 2024, and 2023:

AUDIT COMMITTEE POLICY ON SERVICES PROVIDED BY THE INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Consistent with SEC and NYSE policies regarding auditor independence, the Audit Committee has the responsibility for appointing, setting compensation for and overseeing the work of our independent auditor. In furtherance of this responsibility, the Audit Committee has established a policy with respect to the pre-approvalof audit and permissible non-auditservices provided by our independent auditor. Prior to the engagement of PricewaterhouseCoopers LLP as our independent auditor for the 2025 audit, a plan was submitted to and approved by the Audit Committee setting forth the audit services expected to be rendered during 2025. The plan included audit services, which are comprised of work performed in the audit of our financial statements and to attest and report on our internal controls over financial reporting, as well as work that only the independent auditor can reasonably be expected to provide, including:

Audit fees are budgeted, and the Audit Committee requires the independent auditor and management to report actual fees versus budgeted fees periodically during the year by category of service.

The Audit Committee has adopted a policy that provides that fees for audit, audit related and tax services that are not included in the independent auditor's annual services plan and for services for which fees are not determinable on an annual basis are pre-approvedif the fees for such services will not exceed $75,000. In addition, the policy provides that the Audit Committee may delegate pre-approvalauthority to one or more of its members. The member to whom such authority is delegated must report, for informational purposes only, any pre-approvaldecisions to the Audit Committee at its next scheduled meeting.

2025 REPORT OF THE AUDIT COMMITTEE

The purpose of the Audit Committee is to assist the Board with the oversight of the integrity of the company's financial statements and internal controls, the company's compliance with legal and regulatory requirements, the independence, qualifications and performance of the company's independent registered public accounting firm and the performance of the company's internal audit function. The Audit Committee's function is more fully described in its charter, which the Board has adopted. The charter is on and may be printed from our website at www.onegas.comand is also available from the company's corporate secretary upon request. The Audit Committee reviews the charter on an annual basis. The Board annually reviews the definition of "independence" for audit committee members contained in the listing standards for the NYSE and applicable rules of the SEC, as well as our director independence guidelines, and has determined that each member of the Audit Committee is independent under those standards. In addition, the Board has determined that all members of the Audit Committee are financially literate, and five of the seven committee members are audit committee financial experts.

Management is responsible for the preparation, presentation and integrity of the company's financial statements, accounting and financial reporting principles, internal controls and procedures designed to ensure compliance with accounting standards, applicable laws and regulations. The company's independent registered public accounting firm, PricewaterhouseCoopers LLP, is responsible for performing an independent audit of the company's consolidated financial statements and the company's internal control over financial reporting and expressing an opinion on the conformity of those financial statements with generally accepted accounting principles and on the effectiveness of the company's internal control over financial reporting.

In this context, the Audit Committee has met and held discussions with management and the company's independent registered public accounting firm, PricewaterhouseCoopers LLP, regarding the fair and complete presentation of the company's financial results and management's report on its assessment of the company's internal control over financial reporting. In addition, the Audit Committee reviews the quality of the company's significant accounting policies and presentations in the financial statements. The Audit Committee has discussed the company's most critical estimates and accounting policies in its financial statements, as well as alternative treatments. The Audit Committee has also reviewed both the internal and independent auditors' audit plans and subsequent findings. Management has represented to the Audit Committee that the company's consolidated financial statements were prepared in accordance with generally accepted accounting principles, and the Audit Committee has reviewed and discussed the consolidated financial statements with management and the independent auditor.

The Audit Committee has also reviewed and discussed with both management and the independent registered public accounting firm, management's assessment of the company's internal control over financial reporting. In addition, the Audit Committee has discussed the independent auditor's report on the company's internal control over financial reporting. The Audit Committee has also discussed with the company's independent auditor the matters required to be discussed by the applicable requirements of the Public Company Accounting Oversight Board and the SEC.

In addition, the Audit Committee has discussed with the independent registered public accounting firm, the firm's independence from the company and its management, including the matters in the written disclosures and the letter received from PricewaterhouseCoopers LLP as required by the applicable requirements of the Public Company Accounting Oversight Board (United States) regarding the independent accountant's communications with the Audit Committee concerning independence. In 2024, PricewaterhouseCoopers LLP provided federal tax compliance and planning advice of $87,600 to the company, which did not impact the Audit Committee's determination of PricewaterhouseCoopers LLP's independence. No non-auditservices were provided by PricewaterhouseCoopers LLP in 2024 or 2023, and did not impact the Audit Committee's determination of PricewaterhouseCoopers LLP's independence. The Audit Committee will also consider in the future whether the provision of non-auditservices to the company by PricewaterhouseCoopers LLP is compatible with maintaining that firm's independence. The Audit Committee has concluded that the independent registered public accounting firm is independent of the company and its management. In considering the reappointment of PricewaterhouseCoopers LLP as the company's independent registered public accounting firm, the Audit Committee considered talent and experience in the audit engagement, the appropriateness of fees and the quality and candor of communications with the Audit Committee.

The Audit Committee discussed with the company's internal and independent auditors the overall scope and plans for their respective audits. The Audit Committee meets with both the internal and independent auditors, with and without management present, to discuss the results of their examinations, the assessments of the company's internal control over financial reporting and the overall quality of the company's financial reporting.

Based on the review and discussions referred to above, the Audit Committee recommended to the Board, and the Board approved, the inclusion of the audited financial statements of the company as of and for the year ended December 31, 2024, in the company's Annual Report on Form 10-Kfor the year ended December 31, 2024, for filing with the SEC.

Respectfully submitted by the members of the Audit Committee of the Board:

Tracy E. Hart, Chair

Deborah A. P. Hersman, Member

Michael G. Hutchinson, Member

Sanjay D. Meshri, Member

Pattye L. Moore, Member

Eduardo A. Rodriguez, Member

Yves C. Siegel, Member

HOLDINGS OF MAJOR SHAREHOLDERS

The following table sets forth the beneficial owners of 5 percent or more of our common stock known to us on March 1, 2025.

HOLDINGS OF OFFICERS AND DIRECTORS

The following table sets forth the number of shares of our common stock beneficially owned as of March 1, 2025, by (1) each director and nominee for director, (2) each of the executive officers named in the Summary Compensation Table for 2024 under the caption "Compensation Discussion and Analysis" in this proxy statement, and (3) all directors and executive officers as a group.