GATX CORP

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No. )

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GATX CORPORATION

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2026 PROXY STATEMENTNotice of Annual Meeting of Shareholdersto be held on April 24, 2026

March 13, 2026

Dear Fellow Shareholders:

On behalf of the Board of Directors, I invite you to attend GATX Corporation’s 2026 Annual Meeting of Shareholders on Friday, April 24, 2026 at 9:00 a.m. Central Time. This year’s annual meeting will be a virtual meeting of shareholders. You will be able to attend the annual meeting online, vote your shares electronically, and submit your questions during the annual meeting by visiting https://meetnow.global/M5WAZJH. The proxy materials for the meeting, which are available for viewing and printing at www.envisionreports.com/GATX, include a notice setting forth the items we expect to address at the meeting, our Proxy Statement, and a copy of our 2025 annual report to our shareholders.

In 2025, GATX’s net income was $333.3 million, or $9.12 per diluted share. Each of our business units contributed to our strong financial results for the year. Rail North America’s lease revenues increased $66 million, or over 6%, from the prior year. Demand for most railcars remained stable despite macroeconomic uncertainty. We continued to extend lease renewal terms at attractive rates while maintaining strong renewal success, and our fleet utilization remained high at 99%. We were also able to capitalize on continued strong secondary market demand to further optimize Rail North America’s railcar fleet.

Our Rail International businesses produced solid operating results despite a challenging market in Europe. Fleet utilization in both Europe and India remained solid, and we continued to experience increases in renewal lease rates for a majority of railcar types in 2025. In Engine Leasing, the Rolls-Royce and Partners Finance (“RRPF”) affiliates and our wholly owned aircraft spare engine portfolio achieved excellent results as robust demand for global passenger air travel continued to drive strong demand for aircraft spare engines.

In 2025, we once again executed on our strategy of investing in economically attractive opportunities in our core businesses, and we believe these investments will continue to drive future earnings growth and attractive returns. We invested over $640 million in our Rail North America business and over $500 million in GATX International. Our engine leasing businesses increased their investments in aircraft spare engines, as we added seven engines to our wholly owned portfolio for over $140 million, while the RRPF affiliates invested over $1.4 billion. In 2025, GATX’s total investment volume exceeded $1.3 billion.

Additionally, on January 1, 2026, we closed the acquisition of Wells Fargo’s rail asset portfolio. The acquisition was completed through a newly formed joint venture with Brookfield Infrastructure Partners L.P. and its institutional partners (“Brookfield”), which acquired approximately 101,000 railcars from Wells Fargo Bank, N.A. for approximately $4.2 billion. Our initial ownership in the joint venture is 30%, with Brookfield owning 70%. We have the option to acquire up to 100% of the joint venture equity over time. Also on January 1, 2026, GATX directly purchased approximately 200 locomotives from Wells Fargo, while Brookfield directly acquired Wells Fargo’s rail and locomotive finance lease portfolio. GATX will serve as manager of the railcars in the joint venture as well as the finance lease portfolio owned by Brookfield. The acquisition significantly expands GATX’s scale and further diversifies our North American railcar portfolio, representing an important milestone for GATX.

Your vote is very important. Whether or not you plan to attend the virtual annual meeting, please ensure that your shares are represented at the meeting by promptly voting and submitting your proxy by internet or telephone or by signing and returning your proxy card, if requested, in the envelope provided. On behalf of the Board of Directors and management, I would like to thank you for your continued support of GATX.

Important Notice Regarding the Availability of Proxy Materials**

**for the Shareholders’ Meeting to be held on April 24, 2026.

The following materials are available at www.envisionreports.com/GATX:

A Notice of Internet Availability of Proxy Materials (the “Notice of Internet Availability”) or the proxy statement, proxy card and annual report are being sent to shareholders beginning on or about March 13, 2026.

GATX 2026 Annual Meeting of Shareholders

Advance Voting Methods and Deadlines

Internet and telephone voting are available 24 hours a day, seven days a week up to these deadlines:●Registered Shareholders—closing of the polls at the virtual annual meeting●Beneficial Owners—11:59 p.m. Eastern Time on April 23, 2026 (after which voting is available online at the virtual annual meeting if properly registered in advance)●Participants in GATX 401(k) Plans—8:00 a.m. Eastern Time on April 22, 2026

By Order of the Board of Directors,

Executive Vice President, General Counsel and Secretary