WASHINGTON, D.C. 20549

FORM 8-K

PURSUANT TO SECTION 13 OR 15(D) OF

THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): November 18, 2025

MARATHON BANCORP, INC.

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (715) 845-7331

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

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 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

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. ☐

The Annual Meeting of Stockholders of Marathon Bancorp, Inc. (the “Company”) was held on November 18, 2025. The matters listed below were submitted to a vote of the stockholders through the solicitation of proxies, and the proposals are described in detail in the Company’s definitive proxy statement filed with the Securities and Exchange Commission on October 15, 2025. All proposals were approved by the Company’s stockholders. The final results of the stockholder vote were as follows:

1. Election of two directors for a three-year term ending in 2028.

2.The ratification of the appointment of Bonadio & Co., LLP as the Company’s independent registered public accounting firm for the fiscal year ending June 30, 2026.

For		Against		Abstain		Broker Non-Votes
2,073,452		12,360		14,179		—

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.