Form 8-K/A PROSPERITY BANCSHARES For: Jul 01

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K/A

(Amendment No. 1)

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): July 1, 2026

PROSPERITY BANCSHARES, INC.

(Exact name of registrant as specified in its charter)

4295 San Felipe

Houston, Texas 77027

(Address of principal executive offices including zip code)

Registrant’s telephone number, including area code: (281) 269-7199

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Explanatory Note

Effective July 1, 2026, Prosperity Bancshares, Inc. (“Prosperity”) completed its acquisition of Stellar Bancorp, Inc., a Texas corporation (“Stellar”), pursuant to the Agreement and Plan of Merger (the “Merger Agreement”) dated as of January 27, 2026, by and between Prosperity and Stellar, as previously disclosed in Prosperity’s Current Report on Form 8-K filed with the U.S. Securities and Exchange Commission (the “SEC”) on July 1, 2026 (the “Original Form 8-K”). Pursuant to the Merger Agreement, Stellar merged with and into Prosperity (the “Merger”), with Prosperity continuing as the surviving corporation in the Merger.

Item 9.01 Financial Statements and Exhibits.

(a) Financial statements of businesses acquired.

The audited consolidated financial statements of Stellar as of December 31, 2025 and 2024, and for each of the fiscal years ended December 31, 2025, 2024 and 2023, and the related notes, are filed as Exhibit 99.1 hereto and incorporated herein by reference.

The unaudited condensed consolidated financial statements of Stellar as of March 31, 2026 and for the three months ended March 31, 2026 and 2025, and the related notes, are filed as Exhibit 99.2 hereto and incorporated herein by reference.

(b) Pro forma financial information.

The unaudited pro forma condensed combined balance sheet of Prosperity as of March 31, 2026, giving effect to the Merger as if it had occurred on March 31, 2026, and the unaudited pro forma condensed combined statements of income of Prosperity for the three months ended March 31, 2026 and for the fiscal year ended December 31, 2025, in each case giving effect to the Merger as if it had occurred on January 1, 2025, are filed as Exhibit 99.3 hereto and incorporated herein by reference.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.