Company: RDPTF
Filing Date: 2025-08-21
Form Type: 6-K
Source: 0001213900-25-079166
Chunk: 0

Company: Radiopharm Theranostics Ltd
Filing Date: 2025-08-21
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 August 2025

Commission File Number: 001-41621

RADIOPHARM THERANOSTICS LIMITED

(Name of Registrant)

Level 3, 62 Lygon Street, Carlton South, Victoria, 3053, Australia

(Address of principal executive office)</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>

Indicate by check mark whether by furnishing the information contained
in this Form, the registrant is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities
Exchange Act of 1934.

<div align='center'>Yes ☐ No
☒</div>

If “Yes” is marked, indicate below the file number assigned
to the registrant in connection with Rule 12g3-2(b): 82-

<div align='center'>RADIOPHARM THERANOSTICS LIMITED

EXPLANATORY NOTE</div>

Radiopharm Theranostics Limited (the “Company”)
published one announcement (the “Public Notice”) to the Australian Securities Exchange on August 21, 2025 titled:

| - | “Radiopharm to host key opinion leader webinar series” |

A copy of the Public Notice is attached as an exhibit to this report
on Form 6-K.

This report on Form 6-K (including the exhibit
hereto) shall not be deemed to be “filed” for purposes of the Securities Exchange Act of 1934, as amended (the “Exchange
Act”) and shall not be incorporated by reference into any filing under the Securities Act of 1933, as amended, except as shall be
expressly set forth by specific reference in such filing.

<div align='center'>1

EXHIBITS</div>

| Exhibit 
 Number  |     | Description                                          |
| 99.1    |     | Radiopharm to host key opinion leader webinar series |