AMEREN CORP

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549​

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SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No. )

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Definitive Proxy Statement

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Soliciting Material under § 240.14a-12

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Ameren Corporation

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March 31, 2026

Dear Fellow Shareholders:

As we reflect on 2025, we do so with deep gratitude and pride in the resilience of our company and communities. Though the year brought

extraordinary challenges, including devastating spring tornadoes, Ameren stood strong for our customers, delivering reliable energy and supporting recovery efforts.

We also maintained strong performance driven by our unwavering focus on executing our company strategy of investing in rate-regulated energy infrastructure, enhancing regulatory frameworks and advocating for responsible energy policies. I’d like to share some highlights of the year in three areas: sustainable growth, reliability and resiliency, and support of those we serve.

Powering Growth

We remain committed to demonstrating sustainable growth for our owners. Ameren’s ability to power growth starts with a caring team and is built on a foundation of solid utility infrastructure and a strong financial position. In 2025, we delivered meaningful earnings per share growth in addition to a 6% increase in our dividend, representing our twelfth consecutive year of increases. We also executed significant capital investments of $4.1 billion, which was in line with the five-year investment plan we announced in February 2025.

Achieving Key Milestones for Energy Reliability and Resilience

Providing reliable energy for our customers today, while keeping rates as low as possible and preparing for tomorrow’s increasing demand and economic development, is fundamental to everything we do at Ameren. Across our service territory, we’ve made strong progress.

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We filed an updated preferred resource plan with the Missouri Public Service Commission (“MoPSC”), outlining the balanced mix of generation resources needed over the next 20 years to support economic expansion, bolster reliability, and create jobs. Consistent with this plan, we filed requests for MoPSC approval of more than 1.4 GW of new generation and energy storage resources, and a new 50-megawatt solar energy center was placed in service in December.

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The passage of Missouri Senate Bill 4 and the MoPSC’s approval of a new large load customer tariff established a strong framework to capture the investment, jobs and economic growth opportunities tied to significant expected increases in electric demand while protecting residential customers from increased costs. With this framework in place, in early 2026, Ameren Missouri was able to sign long-term electric service agreements with customers representing 2.2 gigawatts of demand under its large load customer rate plan.

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In Illinois, we achieved constructive regulatory outcomes in our natural gas delivery service rate review in November, as well as our 2024 multi-year rate plan reconciliation.

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We also continued advancing the estimated $1.3 billion of transmission projects the Midcontinent Independent System Operator (“MISO”) has assigned to Ameren. MISO identified these projects as critical to supporting the reliability and resiliency of our regional energy grid. Our transmission team worked diligently through 2025 to advance this work while preparing to compete for additional projects to be awarded in 2026 and beyond.

Supporting our Customers and Communities

People are at the heart of everything we do at Ameren. Our employees are customers who live and work in the communities we serve, and we do what we can to help those communities thrive.

This was evident in our efforts following severe tornadoes in May 2025. Our Ameren team worked around the clock to restore service safely in close coordination with local communities, who recognized our outstanding work. Beyond service restoration, Ameren continued to support our customers who were most impacted by severe weather.

Over the course of the year, we expanded our commitment to communities by providing more than $11 million in philanthropic funding to over 400 nonprofit organizations across our service territory and contributing over 27,500 coworker volunteer hours, while also supporting our most vulnerable customers through more than $9 million in increased philanthropic donations and bill payment assistance funding to community action agencies.

We will discuss these highlights and more during the upcoming Ameren Corporation 2026 Annual Meeting of Shareholders, which will be held in a virtual-only format on Thursday, May 14, 2026, at 10 a.m. CDT. You are invited to attend.

Details regarding how to participate in the meeting, including how and when to vote and submit questions, are included in this proxy statement along with additional information regarding our board of directors, strategy, business practices and executive compensation programs. Your vote is important, and I encourage you to cast it promptly.

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Ameren’s performance in 2025 is a reflection of our people, our purpose, and our partnership with the communities we serve. We are proud of the progress we’ve made together.

As we look ahead, we remain focused on delivering safe and reliable energy while investing prudently in a more resilient future. Thank you for your continued trust in Ameren.

Sincerely,

Martin J. Lyons, Jr.

Chairman, President and Chief Executive Officer

Notice of Annual Meeting of Shareholders

of Ameren Corporation

Voting Items

Shareholders will also act on other business properly presented to the meeting. The Board of Directors of the Company presently knows of no other business to come before the meeting.

Who Can Vote

If you owned shares of the Company’s common stock at the close of business on March 16, 2026, you are entitled to vote at the Annual Meeting and at any adjournment thereof. To attend, vote and ask questions during the Annual Meeting, you will need the 16-digit control number included on your Notice of Internet Availability of Proxy Materials, on your proxy card, or on any additional voting instructions that accompanied your proxy materials. Online check-in will begin at 9:45 a.m. CDT. Please allow ample time for the online check-in process. Attendance at the Annual Meeting is subject to capacity limits set by the virtual meeting platform provider.

Each share of common stock is entitled to one vote for each director nominee and one vote for each of the other proposals. In general, shareholders may vote prior to the Annual Meeting by telephone, the Internet or mail, or during the Annual Meeting by participating in the virtual meeting. See “ADDITIONAL INFORMATION — Questions and Answers About the Annual Meeting and Voting” for more details regarding how you may vote if you are a registered holder or a beneficial owner of shares held in “street name.”

Date of Mailing

On or about March 31, 2026, we began mailing to certain shareholders a Notice of Internet Availability of Proxy Materials containing instructions on how to access this proxy statement and our annual report and how to vote online. If you received that notice, you will not receive a printed copy of the proxy materials unless you request it by following the instructions for requesting such materials contained on the notice. On or about March 31, 2026, we began mailing the accompanying proxy card to certain shareholders.

By order of the Board of Directors,

David M. Feinberg

Executive Vice President, General Counsel and Secretary

St. Louis, Missouri

March 31, 2026

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