UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

OF THE SECURITIES EXCHANGE ACT OF 1934

For the month of September 2026

Commission File Number: 001-39152

QUANTUM BIOPHARMA LTD.

(Registrant)

1 Adelaide Street East, Suite 801

Toronto, Ontario M5C 2V9

(Address of Principal Executive Offices)

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 ☒ Form 40-F ☐

Information contained in this report

On March 7, 2025, the Registrant issued a press release announcing the cancellation of certain warrants, the grant of stock options, and the closing of a fourth tranche of its debenture offering. A copy of this press release is furnished as Exhibit 99.1 to this Report.

On October 29, 2025, the Registrant issued a press release announcing a non-brokered private placement of class A multiple voting shares and providing related-party and early warning disclosure. A copy of the press release is furnished as Exhibit 99.2 to this Report.

On March 10, 2026, the Registrant issued a press release announcing a proposed non-brokered private placement of convertible debenture units and a proposed settlement of certain indebtedness through the issuance of Class B subordinate voting shares. A copy of the press release is furnished as Exhibit 99.3 to this Report.

On March 11, 2026, the Registrant issued a press release announcing revisions to the terms of its proposed convertible debenture units financing and related debt settlement. A copy of the press release is furnished as Exhibit 99.4 to this Report.

On March 27, 2026, the Registrant issued a press release announcing its audited financial and operational results for the fourth quarter and year ended December 31, 2025. A copy of the press release is furnished as Exhibit 99.5 to this Report.

On April 27, 2026, the Registrant issued a press release announcing the engagement of Senergy Communications Capital Inc. and King Tide Media LLC to provide marketing and investor and shareholder relations services. A copy of the press release is furnished as Exhibit 99.6 to this Report.

On July 7, 2026, the Registrant issued a press release announcing the engagement of FinnCom, Inc. to provide marketing and investor awareness services. A copy of the press release is furnished as Exhibit 99.7 to this Report.

On July 20, 2026, the Registrant issued a press release announcing the proposed settlement of certain indebtedness through the issuance of Class B subordinate voting shares. A copy of the press release is furnished as Exhibit 99.8 to this Report.

On July 30, 2026, the Registrant issued a press release announcing the closing of the debt settlement and the issuance of Class B subordinate voting shares in settlement of the indebtedness. A copy of the press release is furnished as Exhibit 99.9 to this Report.

On August 21, 2026, the Registrant issued a press release announcing the grant of stock options to certain directors, officers, employees and consultants. A copy of the press release is furnished as Exhibit 99.10 to 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.

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