6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

October 15, 2025

Commission File Number 1-10167

WESTPAC BANKING CORPORATION

(Translation of registrant’s name into English)

275 KENT STREET, SYDNEY, NEW SOUTH WALES 2000, AUSTRALIA

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports

under cover of Form 20-F or Form 40-F.

Form 20-F    x    Form 40-F   ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ¨

Incorporation by Reference

The information contained in this Report on Form 6-K, including the information set forth in Exhibit No. 1, but excluding the information set forth in Exhibit No. 2 and Exhibit No. 3 shall be incorporated by reference in the prospectuses relating to the Registrant’s securities contained in the Registrant’s Registration Statements on Form F-3 (File Nos. 333-283007 and 333-283008), as such prospectuses may be amended or supplemented from time to time.

Removal of operational risk capital overlay

Westpac acknowledges the decision by the Australian Prudential Regulation Authority (APRA) to lift its enforceable undertaking and confirm Westpac’s improvement in risk management.

The removal of the $500 million capital overlay will mean Westpac’s Common Equity Tier 1 (CET1) capital ratio will increase by approximately 17 basis points, reflecting a reduction in risk weighted assets of $6,250 million. This change will apply with immediate effect.

Index to Exhibits

Disclosure regarding forward-looking statements

The information contained in this Report on Form 6-K contains statements that constitute “forward-looking statements” within the meaning of section 21E of the U.S. Securities Exchange Act of 1934.

Forward-looking statements are statements that are not historical facts. Forward-looking statements appear in a number of places in this Report and include statements regarding our current intent, belief or expectations with respect to our business and operations, macro and micro economic and market conditions, results of operations and financial condition and performance, capital adequacy and liquidity and risk management, including, without limitation, future loan loss provisions and financial support to certain borrowers, forecasted economic indicators and performance metric outcomes, indicative drivers, climate- and other sustainability-related statements, commitments, targets, projections and metrics, and other estimated and proxy data.

Words such as ‘will’, ‘may’, ‘expect’, ‘intend’, ‘seek’, ‘would’, ‘should’, ‘could’, ‘continue’, ‘plan’, ‘estimate’, ‘anticipate’, ‘believe’, ‘probability’, ‘indicative’, ‘risk’, ‘aim’, ‘outlook’, ‘forecast’, ‘assumption’, ‘projection’, ‘target’, ‘goal’, ‘guidance’, ‘objective’, ‘ambition’ or other similar words, are used to identify forward-looking statements. These statements reflect our current views on future events and are subject to change, certain known and unknown risks, uncertainties and assumptions and other factors which are, in many instances, beyond our control (and the control of our officers, employees, agents and advisors), and have been made based on management’s current expectations or beliefs concerning future developments and their potential effect upon Westpac.

Forward-looking statements may also be made, verbally or in writing, by members of Westpac’s management or Board in connection with this Report. Such statements are subject to the same limitations, uncertainties, assumptions and disclaimers set out in this Report.

There can be no assurance that future developments or performance will align with our expectations or that the effect of future developments on us will be those anticipated. Actual results could differ materially from those we expect or which are expressed or implied in forward-looking statements, depending on various factors including, but not limited to, those described in the section titled ‘Risk factors’ in Westpac’s 2025 Interim Financial Results on Form 6-K filed with the U.S. Securities and Exchange Commission. When relying on forward-looking statements to make decisions with respect to us, investors and others relying on information in this Report should carefully consider such factors and other uncertainties and events.

Except as required by law, we assume no obligation to revise or update any forward-looking statements in this Report, whether from new information, future events, conditions or otherwise, after the date of this Report.

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, thereunto duly authorized.

Exhibit 1

ASX RELEASE

15 October 2025

Removal of operational risk capital overlay

Westpac acknowledges the decision by the Australian Prudential Regulation Authority (APRA) to lift its enforceable undertaking and confirm Westpac’s improvement in risk management.

This completes a period of significant risk transformation, delivered through our Customer Outcomes and Risk Excellence Program (CORE).

Upon delivery of the Program last year, independent reviewer Promontory noted “The depth of change to the organisation, both structurally and culturally, means that Westpac is now a simpler, stronger bank.”

Westpac CEO Anthony Miller said: “Risk management is one of our five priorities and this year we’ve been focused on embedding the improvement to our risk culture. We can never forget the errors of the past and the importance of the work we have done over the past six years.”

“The positive changes in how we manage risk must now be maintained and continually strengthened. I’m grateful to all of our people who have contributed to our substantial improvement in risk management.”

The removal of the $500 million capital overlay will mean Westpac’s Common Equity Tier 1 (CET1) capital ratio will increase by approximately 17 basis points, reflecting a reduction in risk weighted assets of $6,250 million. This change will apply with immediate effect.

For further information:

This document has been authorised for release by Tim Hartin, Company Secretary.

WESTPAC BANKING CORPORATION ABN 33 007 457 141