ATI INC

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

(Rule

14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant To Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐

Check the appropriate box:

AND NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

anywhere.

Proven to perform

2026 proxy statement

Who we are.

ATI is a global producer of high performance materials and solutions for

the aerospace and defense markets, with emerging opportunities for

specialty energy.

Built on the strong foundation of our legacy companies, we are a global

market-driven powerhouse: advanced, innovative, highly sophisticated

and quality driven.

When you need materials to go further and faster, in the most

extreme conditions, ATI is Proven to Perform.

Core Markets

DEFENSE

Our materials power and protect the

armed services in the air, sea and on

the ground, and help to push the

limits of space.

AEROSPACE

You can’t fly without ATI — our

materials are on virtually every

commercial aircraft flying

today — engines and air frames.

SPECIALTY ENERGY

Our alloys fuel electrical energy in

nuclear reactors, renewables, and

land-based turbines. Our oil and gas

materials fight heat and corrosion

deep in the sea.

ATI Inc. 2021 McKinney Avenue Dallas, TX 75201

Dear Stockholders

I am pleased to invite you to attend ATI’s 2026 Annual Meeting of Stockholders.

As I approach two years as ATI’s President and CEO, I am confident in ATI’s direction and the progress we are making. Over the past several years, we have sharpened our strategic focus, strengthened our financial profile and positioned ATI to deliver sustained long-term value.

In 2025, ATI delivered $4.6 billion in revenue—our highest level in 14 years. We have transformed tremendously over that time. Today, we are a fundamentally different and significantly more profitable business. Most importantly, through disciplined execution, we have exceeded profit and cash flow expectations, improved operational reliability, and strengthened customer relationships, gaining share in our highest value markets. These results reflect a clear strategy and a team committed to execution and accountability.

Our evolution into a focused aerospace and defense leader continues to gain momentum. Aerospace and defense represented 68% of full-year sales in 2025, surpassing our prior 65% target. We participate in every major commercial airframe and engine program and continue to expand our presence across critical defense platforms. Demand for mission-critical materials remains robust, and our differentiated capabilities position ATI as a strategic supplier across long-cycle programs and next-generation technologies.

To meet demand responsibly, we are maintaining a return-focused approach to capital allocation. Beginning in 2024, we expanded titanium melt capacity, supported by customer commitments. We are now advancing disciplined growth plans in highly differentiated nickel melt capacity. Each investment is evaluated through a rigorous return framework designed to enhance competitive advantage while preserving balance sheet strength and financial flexibility.

Beyond aerospace and defense, we are selectively pursuing opportunities in other high-value markets where ATI’s capabilities create clear differentiation. Nuclear and specialty energy markets represent promising areas for growth. While a smaller portion of our portfolio today, this business is scaling quickly as demand for AI-driven infrastructure accelerates. Our capabilities in zirconium, hafnium and other specialty alloys position ATI as a trusted and technically advantaged supplier in these applications.

Across all of our growing markets, one thing is clear: our customers value the execution, quality and reliability we deliver. Our commitment is to deliver mission-critical materials safely, consistently and efficiently, while continuously improving how we operate.

We are equally committed to disciplined shareholder stewardship. In 2025, while continuing to invest in high-return growth initiatives, we repurchased $470 million of our outstanding shares. Our capital allocation strategy balances reinvestment for growth with prudent returns to stockholders and continued financial strength.

ATI’s stock performance over the past several years reflects sustained operational progress across multiple performance cycles. As illustrated in this Proxy Statement, we are outpacing markets and peers in driving standout returns over time. A $100 investment in ATI at the outset of 2022 is worth over $900 as of the record date for the Annual Meeting and has grown by more than 160% just since the beginning of 2025.

Our team, guided by our culture and core values, is committed to continued success. With each goal met, they strive to set the bar higher. We do what we say we’re going to do, when we say we’re going to do it, in the right way. These values permeate our culture, driving shareholder value creation, a commitment to investor outreach, robust corporate governance and my commitment to developing and supporting our team.

At the conclusion of the Annual Meeting, I will assume the role of Board Chair. I appreciate Bob Wetherbee’s service during his tenure and his role in supporting ATI’s strategic repositioning. We will continue building on that progress with disciplined execution and a clear focus on long-term value creation. On behalf of the ATI team, thank you for your trust and support of ATI.

Notice of Annual Meeting

of Stockholders

Annual Meeting Information

DATE & TIME: Thursday, May 14, 2026 11:30 a.m. Central Time

Agenda

compensation of our named

executive officers; and

Young LLP as our independent

auditors for 2026.

Your vote is important Please vote as soon as possible. You can help us reduce expenses and obtain a quorum to conduct business at the Annual Meeting by voting your shares in advance by telephone or internet. How to vote

Via the internet Visit thewebsite listed on ourproxy card

By mail Sign, date and returnyour proxy card in theenclosed envelope

By telephone Call thetelephone number on yourproxy card

During the Virtual Meeting Attend the Annual Meetingwhich is being presentedvirtually via webcast and voteonline during the meeting

Admission to the Meeting

You are entitled to participate, vote and submit questions at ATI Inc.’s virtual 2026 Annual Meeting if you were a stockholder of record as of the close of business on March 16, 2026 or you hold a legal proxy for the meeting provided by your bank, broker or nominee.

Stockholders of Record. You will be able to participate, vote electronically and submit questions during the live webcast of the 2026 Annual Meeting without advance registration. To access the live webcast of the meeting, you will need the 15-digit control number on the proxy card or the “Notice Regarding the Availability of Proxy Materials” (the “Notice”) you previously received.

Beneficial Owners. If you are a beneficial owner and hold your shares through an intermediary, such as a bank, broker, or nominee, you must register in advance to participate in, vote electronically at, or submit questions during the live webcast of the 2026 Annual Meeting. To register in advance, you must obtain a legal proxy from the bank, broker or other nominee that holds your shares giving you the right to vote the shares. Please forward a copy of the legal proxy, along with your email address, to Computershare Trust Company, N.A. (“Computershare”) by email atlegalproxy@computershare.com no later than 4:00 p.m. Central Time, on Monday, May 11, 2026. You will receive confirmation of your registration and instructions on how to attend the meeting by email after Computershare receives your registration materials.

Beneficial owners that are unable to register in advance may still attend the 2026 Annual Meeting by visitingwww.meetnow.global/MSSZRJ5 as a “guest” but will not have the option to vote shares electronically or submit questions during the live webcast of the meeting. However, you may submit questions in advance of the meeting by emailing your question, along with proof of ownership, to investors@ATlmaterials.com.

Our Proxy Statement and 2025 Annual Report are available for review by stockholders of record atenvisionreports.com/ATI and by beneficial owners atedocumentreview.com/ATI. For further information about ATI, please visit our website atatimaterials.com. This Proxy Statement is first being provided to our stockholders on or about March 24, 2026.

On behalf of the Board of Directors:

Amanda J. Skov

Corporate Secretary

March 24, 2026

Important notice regarding the availability of proxy materials for the ATI Annual Meeting of Stockholders to be held on Thursday, May 14, 2026.

As permitted under applicable Securities and Exchange Commission (“SEC”) rules, we are mailing our stockholders a Notice of Internet Availability of Proxy Materials containing instructions on how to access our proxy materials and submit proxy votes online. Our Proxy Statement, proxy card and 2025 Annual Report are available for review at: envisionreports.com/ATI.