Constellation Energy files 424B4: prospectus (424B)

PROSPECTUS SUPPLEMENT to Prospectus Dated January 7, 2026

Common Stock

The Selling Shareholders identified in this prospectus supplement are offering 11,000,000 shares of our common stock, without par value (our “Common Stock”). We will not receive any of the proceeds from the sale of shares of our Common Stock by the Selling Shareholders. See “ Description of Capital Stock ” beginning on page S-11 of this prospectus supplement for a more complete description of the shares offered hereby.

Subject to, and substantially concurrently with, the completion of this offering, we intend to purchase from the underwriters 2,000,000 shares of our Common Stock that are the subject of this offering at the price paid to the Selling Shareholders by the underwriters in this offering. We refer to this proposed repurchase as the “Share Repurchase.” The closing of this offering is not conditioned upon the completion of the Share Repurchase, and the closing of the Share Repurchase is contingent on the closing of this offering.

Following the completion of this offering and the Share Repurchase, we do not expect any shareholder who received shares in connection with our acquisition of Calpine Corporation to beneficially own such shares in an amount that exceeds 4.04% or 3.78% of our shares of Common Stock excluding or including exercise of the option to purchase additional shares, respectively.

Our Common Stock is listed on the Nasdaq Stock Market LLC (the “Nasdaq”) under the symbol “CEG.” On May 29, 2026, the last sale price of our Common Stock as reported on the Nasdaq was $287.75 per share.

Investing in the Common Stock involves risks that are described in the “Risk Factors” section beginning on page S-4 of this prospectus supplement and under similar headings in the documents incorporated by reference into this prospectus supplement and the accompanying prospectus.

We refer you to “ Underwriting ” in this prospectus supplement for additional information regarding underwriting compensation.

The Selling Shareholders have granted the underwriters an option to purchase up to an additional 1,350,000 shares of Common Stock at the public offering price, less the underwriting discount for a period of 30 days following the date of this prospectus supplement.

The shares will be ready for delivery on or about June 2, 2026.