Basis of Presentation (Policies)	6 Months Ended
Dec. 31, 2025
Basis of Presentation
Basis of Presentation	Marathon Bancorp, Inc. (the “Company” or “Marathon Bancorp”), a Maryland corporation, was formed in December 2020 to serve as the mid-tier holding company for Marathon Bank (the “Bank”) upon the completion of the Bank’s mutual holding company reorganization and offering. On April 14, 2021, the Bank completed its reorganization into the mutual holding company structure and the related stock offering of the Company, the Bank’s new holding company. As a result of the reorganization, the Bank became a wholly-owned subsidiary of the Company, the Company issued and sold 45.0% of its outstanding shares of common stock in its stock offering to the public, and the Company issued 55.0% of its outstanding shares of common stock to Marathon MHC (“Mutual Holding Company”), which was the Company’s mutual holding company. On April 21, 2025, the Company completed its conversion from the mutual holding company form of organization to the stock holding company form of organization (the "Conversion"). In connection with the Conversion, the Mutual Holding Company ceased to exist. Also, as part of the Conversion, the Company sold 1,693,411 shares of its common stock, which included 135,472 shares issued to the Employee Stock Ownership Plan (“ESOP”) at a price of $10.00 per share to the public. Each outstanding share of Company common stock owned by the public stockholders of the Company (stockholders other than the Mutual Holding Company) were converted into new shares of Company common stock based on an exchange ratio of 1.3728-to-1. Following the completion of the Conversion, the Company’s shares of common stock began trading on the Nasdaq Capital Market under the trading symbol “MBBC.” The Company generated gross proceeds of $16.9 million from the Conversion. Offering expenses in connection with the Conversion were $1.7 million which were netted against the gross proceeds. In connection with the Conversion, the Company provided a term loan to the ESOP to finance the ESOP’s purchase of the 135,472 shares noted above. The Company combined its existing outstanding ESOP loan in the amount of $777,212 with this new loan resulting in a new term loan to the ESOP of $2.1 million which will be repaid in annual installments over 25 years. Finally, as a result of the Conversion, all existing stock options and restricted stock awards outstanding on April 21, 2025 were adjusted based on the exchange ratio of 1.3728-to-1. All historical share and per share information prior to the completion of the Conversion also has been restated to reflect the 1.3728-to-1 exchange ratio. The Bank is a Wisconsin stock savings bank, which conducts its business through five facilities. The Bank operates as a full-service financial institution with a primary market area including, but not limited to, Marathon County, Ozaukee County and Waukesha County, Wisconsin. Its primary deposit products are demand deposits, savings, and certificates of deposits; and its primary lending products are commercial real estate, commercial and industrial, construction, one-to-four-family residential, multi-family real estate and consumer loans. In addition, the Bank has two nonbank subsidiaries for the purpose of temporarily holding a foreclosed property pending the liquidation of this property and to hold the real estate of its recently opened branch in Brookfield, Wisconsin. The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Actual results may differ from those estimates, and such differences could be material to the financial statements. Material estimates that are particularly susceptible to significant changes in the near term relate to the determination of the allowance for credit losses, valuation of foreclosed assets, valuation of deferred tax assets, and fair value of financial assets and liabilities. In the opinion of management, all adjustments considered necessary for fair presentation have been included. Operating results for the three and six month periods ended December 31, 2025 are not necessarily indicative of the results for the fiscal year ending June 30, 2026 or any other period. For further information, refer to the audited consolidated financial statements and notes thereto for the fiscal years ended June 30, 2025 and 2024 contained in the Company’s Annual Report on Form 10-K as filed with the Securities and Exchange Commission on September 26, 2025.
Recent Accounting Pronouncements	Recent Accounting Pronouncements This section provides a summary description of recent Accounting Standards Updates (ASU) issued by the Financial Accounting Standards Board (FASB) to the Accounting Standards Codification (ASC) that had or that management expects may have an impact on the consolidated financial statements issued upon adoption. The Company is classified as an emerging growth company and has elected 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. Effective dates reflect this election. Recently Issued, But Not Yet Effective Accounting Pronouncements In November 2024, the Financial Accounting Standards Board (FASB) issued ASU 2024-03, “Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses.” ASU 2024-03 requires public companies to disclose, in the notes to the financial statements, specific information about certain costs and expenses at each interim and annual reporting period. This includes disclosing amounts related to employee compensation, depreciation, and intangible asset amortization. In addition, public companies will need to provide qualitative description of the amounts remaining in relevant expense captions that are not separately disaggregated quantitatively. In January 2025, the FASB issued ASU No. 2025-01 clarifying the effective date for public business entities for fiscal years beginning after December 15, 2026 and interim periods within annual reporting periods beginning after December 15, 2027. Early adoption is permitted. The Company is evaluating ASU 2024-03 and its impact on its disclosures. In December 2023, the Financial Accounting Standards Board (FASB) issued ASU 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures.” The amendments in this ASU require an entity to disclose specific categories in the rate reconciliation and provide additional information for reconciling items that meet a quantitative threshold, which is greater than five percent of the amount computed by multiplying pretax income by the entity’s applicable statutory rate, on an annual basis. Additionally, the amendments in this ASU require an entity to disclose the amount of income taxes paid (net of refunds received) disaggregated by federal, state, and foreign taxes and the amount of income taxes paid (net of refunds received) disaggregated by individual jurisdictions that are equal to or greater than five percent of total income taxes paid (net of refunds received). Lastly, the amendments in this ASU require an entity to disclose income (or loss) from continuing operations before income tax expense (or benefit) disaggregated between domestic and foreign and income tax expense (or benefit) from continuing operations disaggregated by federal, state, and foreign. This ASU is effective for annual periods beginning after December 15, 2024. Early adoption is permitted. The amendments should be applied on a prospective basis; however, retrospective application is permitted. The Company does not expect the adoption of ASU 2023-09 to have a material impact on its consolidated financial statements.

Basis of Presentation (Policies)

6 Months Ended

Dec. 31, 2025

Marathon Bancorp, Inc. (the “Company” or “Marathon Bancorp”), a Maryland corporation, was formed in December 2020 to serve as the mid-tier holding company for Marathon Bank (the “Bank”) upon the completion of the Bank’s mutual holding company reorganization and offering.

On April 14, 2021, the Bank completed its reorganization into the mutual holding company structure and the related stock offering of the Company, the Bank’s new holding company. As a result of the reorganization, the Bank became a wholly-owned subsidiary of the Company, the Company issued and sold 45.0% of its outstanding shares of common stock in its stock offering to the public, and the Company issued 55.0% of its outstanding shares of common stock to Marathon MHC (“Mutual Holding Company”), which was the Company’s mutual holding company.

On April 21, 2025, the Company completed its conversion from the mutual holding company form of organization to the stock holding company form of organization (the "Conversion"). In connection with the Conversion, the Mutual Holding Company ceased to exist. Also, as part of the Conversion, the Company sold 1,693,411 shares of its common stock, which included 135,472 shares issued to the Employee Stock Ownership Plan (“ESOP”) at a price of $10.00 per share to the public. Each outstanding share of Company common stock owned by the public stockholders of the Company (stockholders other than the Mutual Holding Company) were converted into new shares of Company common stock based on an exchange ratio of 1.3728-to-1. Following the completion of the Conversion, the Company’s shares of common stock began trading on the Nasdaq Capital Market under the trading symbol “MBBC.”

The Company generated gross proceeds of $16.9 million from the Conversion. Offering expenses in connection with the Conversion were $1.7 million which were netted against the gross proceeds.

In connection with the Conversion, the Company provided a term loan to the ESOP to finance the ESOP’s purchase of the 135,472 shares noted above. The Company combined its existing outstanding ESOP loan in the amount of $777,212 with this new loan resulting in a new term loan to the ESOP of $2.1 million which will be repaid in annual installments over 25 years.

Finally, as a result of the Conversion, all existing stock options and restricted stock awards outstanding on April 21, 2025 were adjusted based on the exchange ratio of 1.3728-to-1. All historical share and per share information prior to the completion of the Conversion also has been restated to reflect the 1.3728-to-1 exchange ratio.

The Bank is a Wisconsin stock savings bank, which conducts its business through five facilities. The Bank operates as a full-service financial institution with a primary market area including, but not limited to, Marathon County, Ozaukee County and Waukesha County, Wisconsin. Its primary deposit products are demand deposits, savings, and certificates of deposits; and its primary lending products are commercial real estate, commercial and industrial, construction, one-to-four-family residential, multi-family real estate and consumer loans. In addition, the Bank has two nonbank subsidiaries for the purpose of temporarily holding a foreclosed property pending the liquidation of this property and to hold the real estate of its recently opened branch in Brookfield, Wisconsin.

The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Actual results may differ from those estimates, and such differences could be material to the financial statements. Material estimates that are particularly susceptible to significant changes in the near term relate to the determination of the allowance for credit losses, valuation of foreclosed assets, valuation of deferred tax assets, and fair value of financial assets and liabilities.

In the opinion of management, all adjustments considered necessary for fair presentation have been included. Operating results for the three and six month periods ended December 31, 2025 are not necessarily indicative of the results for the fiscal year ending June 30, 2026 or any other period. For further information, refer to the audited consolidated financial statements and notes thereto for the fiscal years ended June 30, 2025 and 2024 contained in the Company’s Annual Report on Form 10-K as filed with the Securities and Exchange Commission on September 26, 2025.

Recent Accounting Pronouncements

Recent Accounting Pronouncements

This section provides a summary description of recent Accounting Standards Updates (ASU) issued by the Financial Accounting Standards Board (FASB) to the Accounting Standards Codification (ASC) that had or that management expects may have an impact on the consolidated financial statements issued upon adoption. The Company is classified as an emerging growth company and has elected 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. Effective dates reflect this election.

Recently Issued, But Not Yet Effective Accounting Pronouncements

In November 2024, the Financial Accounting Standards Board (FASB) issued ASU 2024-03, “Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses.” ASU 2024-03 requires public companies to disclose, in the notes to the financial statements, specific information about certain costs and expenses at each interim and annual reporting period. This includes disclosing amounts related to employee compensation, depreciation, and intangible asset amortization. In addition, public companies will need to provide qualitative description of the amounts remaining in relevant expense captions that are not separately disaggregated quantitatively. In January 2025, the FASB issued ASU No. 2025-01 clarifying the effective date for public business entities for fiscal years beginning after December 15, 2026 and interim periods within annual reporting periods beginning after December 15, 2027. Early adoption is permitted. The Company is evaluating ASU 2024-03 and its impact on its disclosures.

In December 2023, the Financial Accounting Standards Board (FASB) issued ASU 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures.” The amendments in this ASU require an entity to disclose specific categories in the rate reconciliation and provide additional information for reconciling items that meet a quantitative threshold, which is greater than five percent of the amount computed by multiplying pretax income by the entity’s applicable statutory rate, on an annual basis. Additionally, the amendments in this ASU require an entity to disclose the amount of income taxes paid (net of refunds received) disaggregated by federal, state, and foreign taxes and the amount of income taxes paid (net of refunds received) disaggregated by individual jurisdictions that are equal to or greater than five percent of total income taxes paid (net of refunds received). Lastly, the amendments in this ASU require an entity to disclose income (or loss) from continuing operations before income tax expense (or benefit) disaggregated between domestic and foreign and income tax expense (or benefit) from continuing operations disaggregated by federal, state, and foreign. This ASU is effective for annual periods beginning after December 15, 2024. Early adoption is permitted. The amendments should be applied on a prospective basis; however, retrospective application is permitted. The Company does not expect the adoption of ASU 2023-09 to have a material impact on its consolidated financial statements.