Filed Pursuant to Rule 424(b)(3)
Registration No. 333-263798

PROSPECTUS SUPPLEMENT NO. 4

(To Prospectus dated June 1, 2022)

UP TO 19,354,059 SHARES OF COMMON STOCK

ISSUABLE UPON EXERCISE OF WARRANTS

UP TO 96,941,181 SHARES OF COMMON STOCK

UP TO 4,450,000 WARRANTS TO PURCHASE COMMON STOCK

This prospectus supplement supplements the prospectus, dated June 1, 2022 (the “Prospectus”), which forms a part of our registration statement on Form S-1 (No. 333-263798). 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 September 16, 2022 (the “Current Report”). Accordingly, we have attached the Current Report to this prospectus supplement.

The Prospectus and this prospectus supplement relate to the issuance by us of up to an aggregate of 19,354,059 shares of our common stock, $0.0001 par value per share (the “common stock”) consisting of (i) 4,450,000 shares of common stock issuable upon the exercise of 4,450,000 warrants (the “private placement warrants”) originally issued in a private placement in connection with the initial public offering (the “IPO”) of Supernova Partners Acquisition Company II, Ltd., a Cayman Islands exempted company (“Supernova”), by the holders thereof, (ii) 8,624,972 shares of common stock issuable upon the exercise of 8,624,972 warrants (the “public warrants” and, together with the private placement warrants, the “warrants”) originally issued in the IPO by holders thereof, and (iii) 6,279,087 shares of common stock issuable upon the exercise of warrants assumed by us and converted into warrants to purchase common stock (the “Rigetti assumed warrants”) in connection with the Business Combination (as defined below). We will receive the proceeds from the exercise of any warrants and any Rigetti assumed warrants for cash.

The Prospectus and this prospectus supplement also relate to the offer and sale from time to time by the selling securityholders named in this prospectus or their permitted transferees (the “selling securityholders”) of up to (i) 96,941,181 shares of common stock consisting of (a) 10,251,000 shares of common stock purchased by subscribers at a price of $10.00 per share and 4,390,244 shares of common stock purchased by subscribers at a price of $10.25 per share in private placements pursuant to separate subscription agreements, (b) 8,625,000 shares of common stock (the “Founder Shares”) originally purchased by Supernova Partners II LLC (“Supernova Sponsor”) for $25,000, or for approximately $0.004 per share, in a private placement in connection with the IPO, including 3,059,273 Founder Shares subject to vesting and forfeiture (the “Sponsor Vesting Shares”), (c) 4,450,000 shares of common stock issuable upon exercise of the private placement warrants, (d) 2,446,716 shares of common stock issuable pursuant to the exercise of Rigetti assumed warrants, which Rigetti assumed warrants have a weighted average exercise price of $0.6628 per share, (e) 6,226,065 shares of common stock issuable upon exercise of outstanding options, which have an exercise price of $0.272 per share, (f) 6,288,369 shares of common stock issuable in connection with the vesting and settlement of outstanding restricted stock units, which were assumed by and converted into restricted stock awards for common stock in connection with the Business Combination based on an acquiror share value of $10.00 per share and (g) 54,263,787 shares of common stock issued in connection with the Business Combination as merger consideration at an acquiror share value of $10.00 per share, and (ii) up to 4,450,000 private placement warrants, which were purchased by Supernova Sponsor at a price of $2.00 per warrant. We will not receive any proceeds from the sale of shares of common stock or warrants by the selling securityholders pursuant to this prospectus.

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.

Our common stock and public warrants are listed on the Nasdaq Capital Market under the symbols “RGTI” and “RGTIW,” respectively. On September 15, 2022, the last reported sales price of our common stock was $2.28 per share and the last reported sales price of our public warrants was $0.264 per warrant.

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 16 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.

Prospectus Supplement dated September 16, 2022.

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): September 16, 2022

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 obligations 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.  ☐

Rigetti Computing, Inc. (the “Company” or “Rigetti”) has announced the following business updates in connection with its previously announced investor presentation being held on September 16, 2022:

Keysight True-Q Error Mitigation Tools on Rigetti Quantum Cloud Services (QCS^™)

Rigetti anticipates the upcoming release of Keysight’s True-Q error mitigation software integrated into Rigetti QCS in the coming months. For Rigetti, this will be the first third party software tool to be integrated directly into the QCS platform, expected to advance the Company’s partnership strategy to accelerate toward quantum advantage.

Collaboration with NVIDIA to Develop Hybrid GPU-QPU Workflow for Climate Modeling

Rigetti is embarking on a new collaboration with NVIDIA to develop a hybrid GPU-QPU workflow for climate modeling applications. The project aims to evaluate the potential for narrow quantum advantage in this research domain by applying quantum machine learning techniques in a high-performance hybrid workflow. The work builds on recent weather modeling application research by Rigetti.

Public Preview of Rigetti Quantum Processors on Microsoft Azure Quantum

Earlier this week, Rigetti announced the release of its Aspen-M-2 80-qubit and Aspen-11 40-qubit in public preview on Azure Quantum. Rigetti’s integration with Azure supports Quil, Rigetti’s native quantum programming language, and Quil-T for pulse level programming. With the Azure announcement, Rigetti is now available on the world’s two largest public cloud platforms.

Performance at Scale: Aiming to Deliver Next-Generation Hardware in 2023

Cautionary Language Concerning Forward-Looking Statements

Certain statements in this communication may be considered forward-looking statements, including statements with respect to expectations for the anticipated launch of the Company’s 84-qubit quantum computer, 336-qubit multi-chip processor, 1,000+ qubit system, and 4,000+ qubit system, including these systems’ timing and potential performance; expectations relating to the Company’s technology roadmap and the timing thereof; expectations with respect to its partnership with Bluefors, including the development of necessary refrigerators to support the Company’s technology roadmap and the timing thereof; expectations with respect to leveraging fourth generation circuit architecture and introducing higher connectivity and tunable coupling, designed to ultimately deliver fidelities exceeding 99%; the timing, capabilities and capacity of the Company’s fab-1 expansion; expectations with respect to the Company’s partnership with NVIDA to evaluate the potential for narrow quantum advantage, including the potential to address climate challenges; expectations with respect to the anticipated release of Keysight’s True-Q error mitigation software integrated into Rigetti QCS in the coming months; expectations with respect to the Company’s goal of delivering performance at scale with the [goal/mission] of being the industry standard and the ability of its strategic investments in quantum hardware, software, and partnerships to enable progress toward Quantum Advantage; and expectations relating to growth of the business, including with respect to future potential government and commercial contracts, development activities and expansion of QCaaS. Forward-looking statements generally relate to future events and can be identified by terminology such as “pro forma,” “may,” “should,” “could,” “might,” “plan,” “possible,” “project,” “strive,” “budget,” “forecast,” “expect,” “intend,” “will,” “estimate,” “believe,” “predict,” “potential,” “pursue,” “aim,” “goal,” “mission,” “outlook,” “anticipate” or “continue,” or the negatives of these terms or variations of them or similar terminology. Such forward-looking statements are subject to risks, uncertainties, and other factors which could cause actual results to differ materially from those expressed or implied by such forward-looking statements. These forward-looking statements are based upon estimates and assumptions that, while considered reasonable by Rigetti and its management, are inherently uncertain. Factors that may cause actual results to differ materially from current expectations include, but are not limited to: Rigetti’s ability to achieve milestones, technological advancements, including with respect to its roadmap, help unlock quantum computing, and develop practical applications; the ability of Rigetti to complete ongoing negotiations with government contractors successfully and in a timely manner; the potential of quantum computing; the ability of Rigetti to obtain government contracts and the availability of government funding; the ability of Rigetti to expand its QCaaS business; the success of Rigetti’s partnerships and collaborations; Rigetti’s ability to accelerate its development of multiple generations of quantum processors; the outcome of any legal proceedings that may be instituted against Rigetti or others; the ability to meet stock exchange listing standards; the risk that the business combination disrupts current plans and operations of Rigetti; the ability to recognize the anticipated benefits of its recent business combination with Supernova, which may be affected by, among other things, competition, the ability of Rigetti to grow and manage growth profitably, maintain relationships with customers and suppliers and retain its management and key employees; costs related to the business combination with Supernova and operating as a public company; changes in applicable laws or regulations; the possibility that Rigetti may be adversely affected by other economic, business, or competitive factors; Rigetti’s estimates of expenses and profitability; the evolution of the markets in which Rigetti competes; the ability of Rigetti to execute on its technology roadmap; the ability of Rigetti to implement its strategic initiatives, expansion plans and continue to innovate its existing services; the impact of the COVID-19 pandemic on Rigetti’s business; the expected use of proceeds from the Company’s past and future financings or other capital; the sufficiency of Rigetti’s cash resources; unfavorable conditions in Rigetti’s industry, the global economy or global supply chain, including financial and credit market fluctuations and uncertainty, rising inflation, increased costs, international trade relations, political turmoil, natural catastrophes, warfare (such as the ongoing military conflict between Russia and Ukraine and related sanctions against Russia), and terrorist attacks; and other risks and uncertainties set forth in the section entitled “Risk Factors” and “Cautionary Note Regarding Forward-Looking Statements” in the registration on Form S-4, the Company’s Form 8-K filed with the Securities and Exchange Commission (the “SEC”) on March 7, 2022, and in the Company’s Form 10-Q for the three months ended March 31, 2022, and other documents filed by the Company from time to time with the SEC, including the Company’s Quarterly Report on Form 10-Q for the three months ended June 30, 2022. These filings identify and address other important risks and uncertainties that could cause actual events and results to differ materially from those contained in the forward-looking statements. Forward-looking statements speak only as of the date they are made. Readers are cautioned not to put undue reliance on forward-looking statements, and the Company assumes no obligation and does not intend to update or revise these forward-looking statements other than as required by applicable law. The Company does not give any assurance that it will achieve its expectations.

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: September 16, 2022