Filed Pursuant to Rule 424(b)(3)
Registration No. 333-266938

PROSPECTUS SUPPLEMENT NO. 3

(To Prospectus dated April 14, 2023)

23,648,889 SHARES OF COMMON STOCK

This prospectus supplement updates and supplements the prospectus, dated April 14, 2023 (as supplemented to date, the “Prospectus”), which forms a part of our registration statement on Form S-1 (No. 333-266938). 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 July 13, 2023 (the “Current Report”). Accordingly, we have attached the Current Report to this prospectus supplement.

The Prospectus and this prospectus supplement relate to the offer and resale of up to 23,648,889 shares of our common stock, $0.0001 per share (the “common stock”), by B. Riley Principal Capital II, LLC (“B. Riley” or the “selling stockholder”). The shares included in the Prospectus consist of shares of common stock that we have issued or that we may, in our discretion, elect to issue and sell to B. Riley, from time to time after the date of the Prospectus, pursuant to a Common Stock Purchase Agreement we entered into with B. Riley on August 11, 2022 (the “Purchase Agreement”), in which B. Riley has committed to purchase from us, at our direction, up to $75,000,000 of our common stock, subject to terms and conditions specified in the Purchase Agreement. Concurrently with our execution of the Purchase Agreement on August 11, 2022, we issued 171,008 shares of common stock to B. Riley as consideration for its irrevocable commitment to purchase shares of our common stock at our election in our sole discretion, from time to time after the date of the Prospectus, upon the terms and subject to the satisfaction of the conditions set forth in the Purchase Agreement. See the section of the Prospectus titled “Committed Equity Financing” for a description of the Purchase Agreement and the section titled “Selling Stockholder” for additional information regarding the selling stockholder.

We are not selling any shares of common stock being offered by the Prospectus and will not receive any of the proceeds from the sale of such shares by B. Riley. However, we may receive up to $75,000,000 in aggregate gross proceeds from sales of our common stock to B. Riley that we may, in our discretion, elect to make, from time to time after the date of the Prospectus, pursuant to the Purchase Agreement.

B. Riley may sell or otherwise dispose of the shares of common stock included in the Prospectus in a number of different ways and at varying prices. See the section of the Prospectus titled “Plan of Distribution (Conflict of Interest)” for more information about how B. Riley may sell or otherwise dispose of the common stock being offered in the Prospectus. B. Riley is an “underwriter” within the meaning of Section 2(a)(11) of the Securities Act of 1933, as amended.

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 is qualified by reference to the Prospectus, including any amendments or supplements thereto, except to the extent that the information in this prospectus supplement updates and supersedes the information contained therein.

The common stock is listed on The Nasdaq Capital Market (“Nasdaq”) under the symbol “RGTI.” On July 12, 2023, the last reported sales price of the common stock as reported on Nasdaq was $1.74 per share.

We are an “emerging growth company” as defined under U.S. federal securities laws and, as such, have elected to comply with reduced public company reporting requirements. The Prospectus complies with the requirements that apply to an issuer that is an emerging growth company.

Investing in our securities involves a high degree of risks. You should review carefully the risks and uncertainties described in the section titled “Risk Factors” beginning on page 20 of the Prospectus, and under similar headings in any amendments or supplements to the Prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or passed upon the accuracy or adequacy of the Prospectus or this prospectus supplement. Any representation to the contrary is a criminal offense.

The date of this prospectus supplement is July 13, 2023.

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

Date of Report (Date of earliest event reported): July 12, 2023

RIGETTI COMPUTING, INC.

(Exact name of registrant as specified in its charter)

(510) 210-5550

(Registrant’s telephone number, including area code)

N/A

(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 (see General Instruction A.2 below):

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. ☐

As previously disclosed, on January 25, 2023, Rigetti Computing, Inc. (the “Company”) received a letter from the Listing Qualifications Department of The Nasdaq Stock Market, LLC (“Nasdaq”) indicating that, based on the closing bid price for the previous 30 consecutive business days, the listing of the Company’s common stock was not in compliance with Nasdaq Listing Rule 5550(a)(2) to maintain a minimum bid price of $1.00 per share (the “Bid Price Rule”). Under Nasdaq Listing Rule 5810(c)(3)(A), the Company had a period of 180 calendar days, or until July 24, 2023, to regain compliance.

On July 12, 2023, the Company received notification from Nasdaq confirming that for the period from June 27, 2023 to July 11, 2023 the closing bid price of the Company’s common stock had been at $1.00 or greater and that accordingly, the Company has regained compliance with the Bid Price Rule and the matter is now closed.

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 hereunto duly authorized.

Dated: July 13, 2023