Company: APM
Filing Date: 2025-09-10
Form Type: 6-K
Source: 0001213900-25-086383
Chunk: 0

Company: Aptorum Group Ltd
Filing Date: 2025-09-10
Form: 6-K
Chunk 0
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<div align='center'>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

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of September 2025

Commission File Number: 001-38764

APTORUM GROUP LIMITED

17 Hanover Square

London W1S 1BN, United Kingdom

(Address of principal executive offices)</div>

Indicate by check mark whether the registrant
files or will file annual reports under cover of Form 20-F or Form 40-F:

<div align='center'>Form 20-F ☒ Form
40-F ☐</div>

As previously disclosed, Aptorum Group Limited,
a Cayman Islands exempted company with limited liability (“Aptorum”, “APM,” “Aptorum Group” or the
“Company”) and DiamiR Biosciences Corp., a Delaware corporation (“DiamiR”), entered into an Agreement and Plan
of Merger on July 14, 2025, (the “Merger Agreement”), pursuant to which, among other matters, Aptorum will form a direct,
wholly owned subsidiary in the state of Delaware (“Merger Sub”), which will merge with and into DiamR, with DiamiR surviving
as a wholly owned subsidiary of Aptorum, and the surviving corporation of the merger with the Merger Sub (the “Merger”).

Later this week, DiamiR will present at the HCW
Conference, during which it will show a presentation about the two companies and the Merger.

<div align='center'>EXHIBIT INDEX</div>

| Exhibit No. |     | Description  |
| 99.1        |     | Presentation |

<div align='center'>1

SIGNATURES</div>

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.

| Date: September 9, 2025 | Aptorum Group Limited 
 By:                   | /s/ Ian Huen |          |
|:------------------------|:----------------------|:-------------|:---------|
|                         |                       | Name:        | Ian Huen |
|                         |                       | Title:       | CEO