Supplemental Prospectus (Form 424B3)

Filed pursuant to Rule 424(b)(3)

Registration No. 333-291832

Prospectus Supplement No. 4

(To Prospectus dated December 11, 2025)

Jupiter Neurosciences, Inc.

This prospectus supplement updates, amends and supplements the prospectus dated December 11, 2025 (the "Prospectus"), which forms a part of our Registration Statement on Form S-1 (Registration No. 333-291832) and is being filed to update, amend and supplement the information included in the Prospectus with information contained in our Current Report on Form 8-K, which was filed with the Securities and Exchange Commission (the "SEC") on May 21, 2026 (the "Current Report"). Accordingly, we have attached the Current Report to this prospectus supplement. Capitalized terms used in this prospectus supplement and not otherwise defined herein have the meanings specified in the Prospectus.

This prospectus supplement is not complete without the Prospectus. This prospectus supplement should be read in conjunction with the Prospectus, which is to be delivered with this prospectus supplement, and is qualified by reference thereto, except to the extent that the information in this prospectus supplement updates or supersedes the information contained in the Prospectus. Please keep this prospectus supplement with your Prospectus for future reference.

Shares of our common stock, par value $0.0001 per share (our "Common Stock"), are listed on The Nasdaq Stock Market, LLC under the symbol "JUNS." On May 20, 2026, the closing price of our Common Stock was $0.2050 per share.

Investing in our securities involves risks that are described in the "Risk Factors" section of the Prospectus.

Neither the SEC nor any state securities commission has approved or disapproved of the securities to be issued under the Prospectus or this prospectus supplement or determined if the Prospectus or this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus supplement is May 21, 2026.