Supplemental Prospectus (Form 424B3)

Filed Pursuant to Rule 424(b)(3)

Registration No. 333-286800

PROSPECTUS SUPPLEMENT NO. 1

(to Prospectus dated April 21, 2026)

SPIRE GLOBAL, INC.

3,162,500 Shares of Class A Common Stock

This prospectus supplement amends and supplements the prospectus dated April 21, 2026 (as supplemented or amended from time to time, the "Prospectus"), which forms a part of our Registration Statement on Form S-1 (No. 333-286800).

This prospectus supplement is being filed to update and supplement the information in the Prospectus with the information contained in our Current Report on Form 8-K, filed with the Securities and Exchange Commission on April 24, 2026 (the "Current Report"). Accordingly, we have attached the Current Report to this prospectus supplement.

This prospectus supplement updates and supplements the information in the Prospectus and is not complete without, and may not be delivered or utilized except in combination with, the Prospectus, including any amendments or supplements thereto. This prospectus supplement should be read in conjunction with the Prospectus and if there is any inconsistency between the information in the Prospectus and this prospectus supplement, you should rely on the information in this prospectus supplement.

Our Class A common stock is traded on the New York Stock Exchange ("NYSE") under the symbol "SPIR." On April 29, 2026, the last quoted sale price for our Class A common stock as reported on NYSE was $15.81 per share.

Investing in our securities involves a high degree of risk. Before buying any securities, you should carefully read the discussion of the risks of investing in our securities in the section titled "Risk Factors" beginning on page 5 of the Prospectus.

You should rely only on the information contained in the Prospectus, this prospectus supplement and any other prospectus supplement or amendment hereto. We have not authorized anyone to provide you with different information.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

The date of this prospectus is May 1, 2026

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

SPIRE GLOBAL, INC.

(Exact name of registrant as specified in its charter)

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.02 Termination of a Material Definitive Agreement.

On April 23, 2026, Spire Global Canada Subsidiary Corp. (the "Company"), a wholly owned subsidiary of Spire Global, Inc., received a written notice terminating for convenience, effective immediately, the contract with His Majesty the King in right of Canada, as represented by the Minister of Public Works and Government Services ("PWGS"), pursuant to which the Company agreed to design and develop the WildFireSat constellation of satellites to monitor wildfires in Canada for the Canadian Space Agency. If all contractual milestones had been achieved, the contract would have had an aggregate value of Can$71.8 million, including harmonized sales tax. No later than May 7, 2026, the Company may submit a settlement proposal with respect to costs arising from the termination of the contract in accordance with the Procedures Information Guide provided by PWGS.

The foregoing description of the contract does not purport to be complete and is qualified in its entirety by reference to the full text of the contract, a copy of which was included as Exhibit 10.1 to the Company's Current Report on Form 8-K filed with the Securities and Exchange Commission on February 7, 2025 and is incorporated by reference herein.

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.