supplement. In accordance with the terms of the Sales Agreement, we may offer and sell shares of our ClassA Common Stock having an aggregate offering price of up to$500,000,000 from time to time through the agents acting as our sales agents pursuant to this prospectus supplement and the accompanying prospectus.Our shares of ClassA Common Stock are listed on The Nasdaq Global Select Market (“Nasdaq”) under the symbol “ASTS.” On May8, 2025, the last reported sale price on Nasdaq of our ClassA Common Stock was $25.25 per share. Sales of our ClassA Common Stock, if any, under this prospectus supplement will be made byany method permitted that is deemed an “at the market offering” as defined in Rule 415 under the Securities Act of 1933, as amended (the “Securities Act”), including sales made directly on or through Nasdaq or any other existing trading market in the United States for our ClassA Common Stock, sales made to or through a marketmaker other than on an exchange or otherwise, directly to the agents as principals, in negotiated transactions (including block trades), at market prices prevailing at thetime of sale or at prices related to such prevailing market prices and/or in any other method permitted by law. If we and the agents agree on any method of distribution number or dollar amount of securities, but each agent has agreed to use its commercially reasonable efforts consistent with its normal trading and sales practices, as oursales agent. There is no arrangement for funds to be received in any escrow, trust or similar arrangement.Each of the agents will be entitled to compensation of up to 3.0% of the gross sales price for any shares of ClassA Common Stock sold through it as a sales agentunder the Sales Agreement, as further described in the “Plan of Distribution” section. In connection with the sale of the ClassA Common Stock on our behalf, each agentmay be deemed to be an “underwriter” within the meaning of the Securities Act, and the compensation of the agents may be deemed to be underwriting commissions or Investing in our ClassA Common Stock involves significant risks. Please read the information contained in or incorporated by referenceunder the heading “Risk Factors” beginning on pageS-10of this prospectus supplement, and under similar headings in other documents filedafter the date hereof and incorporated by reference into this prospectus supplement and the accompanying prospectus for a discussion of thefactors you should carefully consider before deciding to invest in our ClassA Common Stock.Neither the Securities and Exchange Commission nor any state securities commission or other regulatory body has approved or disapproved of ourClassA Common Stock, or determined if this prospectus supplement or the accompanying prospectus is accurate, truthful or complete. Any representation tothe contrary is a criminal offense.B. Riley SecuritiesBarclaysBofA Securities The date of this prospectus supplement is May13, 2025. ABOUT THIS PROSPECTUS SUPPLEMENTCAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS RISK FACTORSUSE OF PROCEEDS Unless the context otherwise requires, references in this prospectus supplement to: •“A&R Operating Agreement” refers to that certain Fifth Amended and Restated Limited Liability Company Operating Agreement ofAST LLC.•“agents” refers to B. Riley Securities, Inc., Barclays Capital Inc., BofA Securities, Inc., Cantor Fitzgerald& Co., Deutsche BankSecurities Inc., Roth Capital Partners, LLC, Scotia Capital (USA) Inc., UBS Securities LLC and William Blair& Company, L.L.C.,collectively.•“American Tower” refers to ATC TRS II LLC, a Delaware limited liability company.•“Antares” refers to Antares Technologies LLC, a Delaware limited liability company.•“AST Equityholders” refers to Avellan, Antares, Vodafone, American Tower and Rakuten USA prior to the Rakuten Transactions and •“AST LLC Common Unit” means a unit of ownership interest in AST LLC, which entitles the holder thereof to the distributions,allocations and other rights under the A&R Operating Agreement.•“AT&T” refers to AT&T Venture Investments, Inc., AT&T Services, Inc. and AT&T, Inc. •“Block 2 BB satellites” refers to our next generation of commercial BB satellites. •“Board of Directors” refers to our board of directors.•“Business Combination” refers to the transactions contemplated by the Equity Purchase Agreement.•“Cellular Broadband” refers to cellular communications at 4G LTE/5G speeds. •“ClassB Common Stock” means the shares of class B common stock, par value $0.0001 per share, of the Company. •“ClassC Share Voting Amount,” as such term is defined in the Charter, means a number of votes per share equal to (i) (x) 88.31%, •“Closing” refers to the completion of the Business Combination. •“Common Stock” refers collectively to ClassA Common Stock, ClassB Common Stock and ClassC Common Stock. S-ii •“Equity Purchase Agreement” refers to that certain Equity Purchase Agreement, dated as of December15, 2020,