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Filed Pursuant to Rule 424(b)(5)
Registration No. 333-297949

PROSPECTUS SUPPLEMENT
(To Prospectus dated August 4, 2026)

Up to $2,266,700,000

Common Stock

We have entered into a sales agreement (as amended, the “sales agreement”) with Barclays Capital Inc., BofA Securities, Inc., Goldman Sachs & Co. LLC, J.P. Morgan Securities LLC, Mizuho Securities USA LLC, Morgan Stanley & Co. LLC, MUFG Securities Americas Inc., RBC Capital Markets, LLC and Wells Fargo Securities, LLC, as our sales agents and as forward sellers as described below, and Bank of America, N.A., Barclays Bank PLC (through its agent Barclays Capital Inc.), Goldman Sachs & Co. LLC, JPMorgan Chase Bank, National Association, Mizuho Markets Americas LLC (with Mizuho Securities USA LLC acting as agent), Morgan Stanley & Co. LLC, MUFG Securities EMEA plc, Royal Bank of Canada and Wells Fargo Bank, National Association, as forward purchasers as described below, relating to the shares of our common stock offered by this prospectus supplement and the accompanying prospectus. The sales agreement relates to shares of our common stock having an aggregate gross sales price of $5,000,000,000, of which shares having an aggregate gross sales price of $2,733,300,000 have previously been sold. In accordance with the terms of the sales agreement, we may, through our sales agents, offer and sell from time to time shares of our common stock having an aggregate gross sales price of up to $2,266,700,000 (unless we increase such aggregate gross sales price in our discretion from time to time pursuant to the sales agreement).

In addition to the issuance and sale of shares of our common stock by us through the sales agents, we also may enter into forward sale agreements under separate master forward sale confirmations and related supplemental confirmations between us and each of Bank of America, N.A., Barclays Bank PLC (through its agent Barclays Capital Inc.), Goldman Sachs & Co. LLC, JPMorgan Chase Bank, National Association, Mizuho Markets Americas LLC (with Mizuho Securities USA LLC acting as agent), Morgan Stanley & Co. LLC, MUFG Securities EMEA plc, Royal Bank of Canada (represented by RBC Capital Markets, LLC) and Wells Fargo Bank, National Association. We refer to these entities, when acting in such capacity, as forward purchasers. In connection with each forward sale agreement, the relevant forward purchaser or its affiliate will, at our request, borrow from third parties and, through the relevant affiliated sales agent, sell a number of shares of our common stock equal to the number of shares of our common stock that underlie the forward sale agreement to hedge the forward sale agreement. We refer to each of Barclays Capital Inc., BofA Securities, Inc., Goldman Sachs & Co. LLC, J.P. Morgan Securities LLC, Mizuho Securities USA LLC, Morgan Stanley & Co. LLC, MUFG Securities Americas Inc., RBC Capital Markets, LLC and Wells Fargo Securities, LLC, when acting as the agent for its affiliated forward purchaser, as a forward seller. In no event will the aggregate number of shares of our common stock sold on or after the date of this prospectus supplement through the sales agents as our agents and by the forward sellers under the sales agreement have an aggregate gross sales price in excess of $2,266,700,000 (unless we increase such aggregate gross sales price in our discretion from time to time pursuant to the sales agreement).

We will not initially receive any proceeds from the sale of borrowed shares of our common stock by a forward seller. We expect to receive proceeds from the sale of shares of our common stock upon future physical settlement of the relevant forward sale agreement with the relevant forward purchaser on dates specified by us on or prior to the maturity date of the relevant forward sale agreement, in which case we would expect to receive aggregate net cash proceeds at settlement equal to the number of shares of our common stock underlying the particular forward sale agreement multiplied by the relevant forward sale price. If we elect to cash settle or net share settle a forward sale agreement, we may not (in the case of cash settlement) or will not (in the case of net share settlement) receive any proceeds, and we may owe cash (in the case of cash settlement) or shares of our common stock (in the case of net share settlement) to the relevant forward purchaser.

Sales of shares of our common stock, if any, under the sales agreement, this prospectus supplement and the accompanying prospectus may be made in sales deemed to be “at the market offerings” as defined in Rule 415 under the Securities Act of 1933, as amended (the “Securities Act”), including sales made directly on or through the New York Stock Exchange (the “NYSE”), or on another market for our common stock, or sales made to or through a market maker other than on an exchange or through an electronic communications network. Subject to the terms and conditions of the sales agreement, the sales agents, forward sellers or forward purchasers will use their commercially reasonable efforts to sell on our behalf all shares of our common stock designated by us from time to time.

We also may sell shares of our common stock in negotiated transactions or as otherwise agreed with the applicable sales agent, forward seller or forward purchaser or to one or more of the sales agents as principal for their own accounts, at a price per share agreed upon at the time of sale. If we sell shares of our common stock in a manner which is not an “at the market offering,” including sales to one or more sales agents, as principal for their own accounts, we will describe the terms of such sale and any agreement relating thereto in a separate prospectus supplement or pricing supplement.

We will pay the sales agents a commission of up to 2% of the gross sales price per share sold through them as our agent under the sales agreement. In connection with each forward sale agreement, the relevant forward seller will receive, reflected in a reduced initial forward sale price payable by the relevant forward purchaser under its forward sale agreement, a commission of up to 2% of the volume weighted average of the gross sales prices of all borrowed shares of our common stock sold during the applicable forward hedge selling period by it as a forward seller. In connection with the sale of shares of our common stock on our behalf, the sales agents, forward sellers and forward purchasers may be deemed to be “underwriters” within the meaning of the Securities Act, and the compensation paid to the sales agents, forward sellers and forward purchasers may be deemed to be underwriting commissions or discounts.

Our common stock is listed on the New York Stock Exchange, or the NYSE, under the symbol “AEE.” The last reported sale price of our common stock on August 3, 2026 was $109.50 per share.

Investing in our common stock involves risks. See “Risk Factors” beginning on page S-5 of this prospectus supplement to read about factors you should consider before buying our common stock.

Neither the Securities and Exchange Commission nor any other regulatory body has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

Barclays

BofA Securities

Goldman Sachs & Co. LLC

J.P. Morgan

Mizuho

Morgan Stanley

MUFG

RBC Capital Markets

Wells Fargo Securities

August 4, 2026

	Page
About this Prospectus Supplement		S-1
Prospectus Supplement Summary		S-2
Risk Factors		S-5
Where You Can Find More Information		S-8
Accounting Treatment		S-9
Use of Proceeds		S-10
Plan of Distribution (Conflicts of Interest)		S-11
Legal Matters		S-16
Experts		S-16

	About this Prospectus					1
	Ameren Corporation					1
	Risk Factors					2
	Where You Can Find More Information					3
	Use of Proceeds					5
	Description of Debt Securities					6
	Description of Common Stock					15
	Description of Preferred Stock					17
	Description of Stock Purchase Contracts and Stock Purchase Units					19
	Book-Entry System					20
	Selling Securityholders					22
	Plan of Distribution					23
	Legal Matters					24
	Experts					24