QT Imaging (QTI) S-4/ARegistration of securities issued in business combination transactions (amended)

The information in this preliminary proxy statement/prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary proxy statement/prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

GIGCAPITAL5, INC.

1731 Embarcadero Rd., Suite 200, Palo Alto, CA 94303

PRELIMINARY PROXY STATEMENT FOR 2023 ANNUAL MEETING OF STOCKHOLDERS

PROSPECTUS FOR 14,807,937 SHARES OF COMMON STOCK OF GIGCAPITAL5, INC.

(WHICH WILL BE RENAMED QT IMAGING HOLDINGS, INC.)

On December 8, 2022, GigCapital5, Inc., a Delaware corporation (“GigCapital5”), and QTI Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of GigCapital5 (“Merger Sub”), entered into a Business Combination Agreement (the “Business Combination Agreement”) with QT Imaging, Inc., a Delaware corporation (“QT Imaging”), pursuant to which, and subject to the approval of the stockholders of GigCapital5, Merger Sub will merge with and into QT Imaging, with QT Imaging surviving the merger as a wholly owned subsidiary of GigCapital5 (the “Merger” and, together with the other transactions contemplated by the Business Combination Agreement and any other agreement executed and delivered in connection therewith, the “Business Combination”). Following the closing of the Merger (the “Closing”), GigCapital5, which will be renamed “QT Imaging Holdings, Inc.”, will be referred to as the “Combined Company.”

Subject to the terms of the Business Combination Agreement, at the effective time of the Merger (the “Effective Time”), each issued and outstanding share of the common stock of QT Imaging, par value $0.001 per share (the “QT Imaging Common Stock”) (excluding each share of QT Imaging Common Stock held in the treasury of QT Imaging which will be cancelled without any conversion of such shares of QT Imaging Common Stock held in the treasury and dissenting shares) will be automatically cancelled and converted into (A) the right to receive a number of shares of common stock, par value $0.0001 per share, of the Combined Company (the “Combined Company Common Stock”) calculated based on the Exchange Ratio (as defined below) and (B) the contingent right to receive a portion of additional shares of Combined Company Common Stock (“Merger Consideration Earnout Shares”) based on the performance of the Combined Company if certain requirements are achieved in accordance with the terms of the Business Combination Agreement, if, as and when payable. The “Exchange Ratio” means the quotient of (a) the Aggregate Closing Merger Consideration (as defined in the Business Combination Agreement) divided by (b) the QT Imaging Fully Diluted Capital Stock (as defined in the Business Combination Agreement). In addition, at the Effective Time, certain warrants of QT Imaging to purchase QT Imaging Common Stock will be converted into a warrant to acquire a number of shares of Combined Company Common Stock at an adjusted exercise price per share.

Only holders of record of GigCapital5 Common Stock, at the close of business on [●], 2023 (the “Record Date”), are entitled to notice of the Stockholders’ Meeting (as defined below) and the right to vote and have their votes counted at the Stockholders’ Meeting and any adjournments of the Stockholders’ Meeting.

In connection with the execution of the Business Combination Agreement, GigCapital5 may enter into agreements with investors for the subscription for GigCapital5 Common Stock, convertible promissory notes or other securities or any combination of such securities to be subscribed for pursuant to the terms of one or more subscription agreements (all such subscription agreements, collectively (the “PIPE Subscription Agreements”) on terms and conditions mutually agreeable to GigCapital5 and QT Imaging (such agreement not to be unreasonably withheld, conditioned or delayed), provided that, unless otherwise agreed to, the aggregate gross proceeds under the PIPE Subscription Agreements will not exceed $26,000,000.

The total number of shares of the Combined Company Common Stock outstanding at the Closing (and each Combined Company stockholder’s relative ownership levels) will be affected by the number of shares of GigCapital5 Common Stock that are redeemed by GigCapital5 public stockholders pursuant to their redemption rights under GigCapital5’s Amended and Restated Certificate of Incorporation, dated as of September 23, 2021 and as amended on September 23, 2022 and further amended on March 28, 2023, in connection with the Business Combination (the “Redemption Rights”).

The table below shows the relative ownership levels of holders of Combined Company Common Stock following the proposed Business Combination under varying redemption scenarios (after giving effect to the election in each of September 2022 and March 2023 of GigCapital5’s public stockholders to partially redeem their shares of GigCapital5 Common Stock pursuant to their Redemption Rights and not including additional dilutive issuances of securities from the exercise of warrants or the issuance of Merger Consideration Earnout Shares).

Upon the Closing, the Combined Company will not be a “controlled company” as defined under the relevant Nasdaq listing rules.

We are providing the accompanying proxy statement/prospectus and accompanying proxy card to our stockholders in connection with the solicitation of proxies to be voted at the 2023 annual meeting of the stockholders (the “Stockholders’ Meeting”), including following any adjournments or postponements of the Stockholders’ Meeting. Information about the Stockholders’ Meeting, the proposed Business Combination and other related business to be considered by our stockholders at the Stockholders’ Meeting is included in this proxy statement/prospectus. Whether or not you plan to attend, we urge you to read this proxy statement/prospectus, in its entirety. In particular, when you consider the recommendation regarding these proposals by the board of directors of GigCapital5, you should keep in mind that the directors and officers of GigCapital5, as well as its largest stockholder, GigAcquisitions5, LLC (the “Sponsor”), have interests in the Business Combination that are different from or in addition to, or which may conflict with, your interests as a stockholder. See the section of the attached proxy statement/prospectus entitled “Meeting of GigCapital5 Stockholders — Recommendation of GigCapital5 Board of Directors” beginning on page 173 for a discussion of these considerations. You should also carefully consider the risk factors described in the section entitled “Risk Factors” beginning on page 64 of the attached proxy statement/prospectus.

GigCapital5’s board of directors has unanimously approved the Business Combination Agreement and the transactions contemplated thereby and recommends that GigCapital5’s stockholders vote “FOR” the adoption and approval of the Business Combination Agreement and the other matters to be considered at the Stockholders’ Meeting.

If you have any questions or need assistance voting your shares, please call our proxy solicitor, Morrow Sodali LLC, toll free at (800) 662-5200.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES REGULATORY AGENCY HAS APPROVED OR DISAPPROVED THE TRANSACTIONS DESCRIBED IN THIS PROXY STATEMENT/PROSPECTUS, PASSED UPON THE MERITS OR FAIRNESS OF THE PROPOSED BUSINESS COMBINATION OR RELATED TRANSACTIONS OR PASSED UPON THE ADEQUACY OR ACCURACY OF THE DISCLOSURE IN THIS PROXY STATEMENT/PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY CONSTITUTES A CRIMINAL OFFENSE.

This proxy statement/prospectus is dated [●], 2023, and is expected to be first mailed or otherwise delivered to GigCapital5 stockholders on or about [●], 2023.

GIGCAPITAL5, INC.

1731 Embarcadero Rd., Suite 200, Palo Alto, California 94303

Dear Stockholder:

On December 8, 2022, GigCapital5, Inc., a Delaware corporation (“GigCapital5”), and QTI Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of GigCapital5 (“Merger Sub”), entered into a Business Combination Agreement (the “Business Combination Agreement”) with QT Imaging, Inc., a Delaware corporation (“QT Imaging”), pursuant to which Merger Sub will merge with and into QT Imaging, with QT Imaging surviving the merger as a wholly owned subsidiary of GigCapital5 (the “Merger” and, together with the other transactions contemplated by the Business Combination Agreement and any other agreement executed and delivered in connection therewith, the “Business Combination”). Following the closing of the Merger (the “Closing”), GigCapital5, which will be renamed “QT Imaging Holdings, Inc.,” will be referred to as the “Combined Company.”

Subject to the terms of the Business Combination Agreement, at the effective time of the Merger (the “Effective Time”), each issued and outstanding share of the common stock of QT Imaging ( the “QT Imaging Common Stock”) (including shares issued upon the exercise or conversion of options to purchase shares of QT Imaging Common Stock that are outstanding as of immediately prior to the Effective Time (the “QT Imaging Options”), warrants of QT Imaging to purchase QT Imaging Common Stock (the “QT Imaging Warrants”) and convertible notes of QT Imaging (the “QT Imaging Convertible Notes”), but excluding each share of QT Imaging Common Stock held in the treasury of QT Imaging which will be cancelled without any conversion of such shares of QT Imaging Common Stock held in the treasury and dissenting shares) will be automatically cancelled and converted into (A) the right to receive a number of shares (the “Per Share Merger Consideration”) of common stock, par value $0.0001 per share, of GigCapital5 (the “GigCapital5 Common Stock”) calculated based on the Exchange Ratio (as defined below) and (B) the contingent right to receive a portion of additional shares of GigCapital5 Common Stock based on the performance of the Combined Company if certain requirements are achieved in accordance with the terms of the Business Combination Agreement, if, as and when payable. The “Exchange Ratio” means the quotient of (a) the Aggregate Closing Merger Consideration (as defined below) divided by (b) the QT Imaging Fully Diluted Capital Stock (as defined below).

The “Aggregate Closing Merger Consideration” means a number of shares of GigCapital5 Common Stock equal to the difference of: (a) the quotient of (i)(A) the sum of (I) $151,000,000, plus (II) the sum of the exercise prices of all In-the-Money Company Warrants (as defined in the Business Combination Agreement), plus (III) the cash of QT Imaging as of immediately prior to the Effective Time (the “QT Imaging Closing Cash”), plus (IV) the transaction expenses of QT Imaging which it will have paid prior to the close of business on the business day immediately preceding the Closing (the “Paid QT Imaging Transaction Expenses”), minus (B) the debt of QT Imaging as of immediately prior to the Effective Time after conversion of any QT Imaging Convertible Notes that are being converted into shares of QT Imaging Common Stock immediately prior to the Effective Time in accordance with the terms of such convertible notes (the “Converting Notes”), and which debt of QT Imaging will not exceed $4,000,000 (the total of the dollar amounts set forth in (a)(i), the “Aggregate Closing Merger Consideration Value”); divided by (ii) $10.00; minus (b) a number of shares of GigCapital5 Common Stock equal to the quotient of (i) the amount of transaction expenses of QT Imaging incurred by or on its behalf in connection with the preparation, negotiation and execution of the Business Combination Agreement and the consummation of the transactions that the Business Combination Agreement contemplates (the “QT Imaging Transaction Expenses”), in excess of $4,000,000, if any, divided by (ii) $10.00, and rounded up to the nearest whole share, and will include all shares to be issued to two entities providing services to QT Imaging as partial payment of the QT Imaging Transaction Expenses for such entities (the number of shares set forth in (b), the “Aggregate Excess QT Imaging Transaction Shares”).

The “QT Imaging Fully Diluted Capital Stock” means, without duplication, the sum of (a) the aggregate number of shares of QT Imaging Common Stock that are issued and outstanding as of immediately prior to the Effective Time (including shares issued upon the exercise or conversion of the QT Imaging Options, the QT

Imaging Warrants and the QT Imaging Convertible Notes, in each case immediately prior to the Effective Time, but excluding each share of QT Imaging Common Stock held in the treasury of QT Imaging which will be cancelled without any conversion of such shares of QT Imaging Common Stock held in the treasury), and (b) the aggregate number of shares of QT Imaging Common Stock issuable upon full exercise, exchange or conversion of all In-the-Money Company Warrants outstanding as of immediately prior to the Effective Time and that will become an Assumed Warrant (the “In-the-Money Company Warrant Shares”). The “Assumed Warrants” are the In-the-Money Company Warrants that are not exercised and exchanged prior to the Effective Time but are instead, without any action on the part of the holder thereof and in accordance with the provisions of such In-the-Money Company Warrant (for the avoidance of doubt, as may be amended following the date of the Business Combination Agreement with the written approval of GigCapital5), converted into a warrant to acquire a number of shares of GigCapital5 Common Stock at an adjusted exercise price per share. The QT Imaging Common Stock, the In-the-Money Company Warrants, the In-The-Money Company Warrant Shares and the shares issued pursuant to the conversion of the Converting Notes (the “QT Imaging Convertible Notes Shares”) will constitute the “QT Imaging Equity Securities”.

In addition, at the Effective Time, GigCapital5 will assume the Assumed Warrants.

Further, prior to the Effective Time, QT Imaging will in a manner acceptable to GigCapital5 take such actions as are necessary to terminate each QT Imaging Option, whether vested or unvested, including by payment or in accordance with the terms of the QT Imaging, Inc. 2021 Stock Incentive Plan, as such may have been amended, supplemented or modified from time to time (the “QT Imaging Option Plan”), without any conversion of such QT Imaging Options, and no payment or distribution will be made, and the holder of any QT Imaging Options will cease to have any rights, with respect to such QT Imaging Options.

GigAcquisitions5, LLC (the “Sponsor”) has agreed to vote its shares of GigCapital5 Common Stock, issued to it prior to GigCapital5’s initial public offering (the “GigCapital5 IPO,” and such shares, the “Founder Shares”), as well as the shares of GigCapital5 Common Stock that are a part of units purchased in a private placement simultaneous to the GigCapital5 IPO, and any Public Shares (as defined below) purchased during or after the GigCapital5 IPO, in favor of the proposed Business Combination.

In connection with the execution of the Business Combination Agreement, GigCapital5 may enter into agreements with investors (the “PIPE Investors”) for the subscription for GigCapital5 Common Stock, convertible promissory notes or other securities or any combination of such securities to be subscribed for pursuant to the terms of one or more subscription agreements (all such subscription agreements, collectively (the “PIPE Subscription Agreements”) on terms and conditions mutually agreeable to GigCapital5 and QT Imaging (such agreement not to be unreasonably withheld, conditioned or delayed), provided that, unless otherwise agreed to, the aggregate gross proceeds under the PIPE Subscription Agreements will not exceed $26,000,000 (the “PIPE Investment Amount”).

As of [●], 2023, the closing price on Nasdaq of the closing price of the Public Shares was $[●] per share, and on the OTC the closing price of the GigCapital5 Units was $[●] per unit, and the closing price of the Warrants was $[●] per warrant.

At the 2023 annual meeting of the stockholders of GigCapital5 (the “Stockholders’ Meeting”), the GigCapital5 stockholders will vote on a proposal to approve the Business Combination Agreement (the “Business Combination Proposal”) and other proposals described in the accompanying proxy statement/prospectus, which each stockholder is encouraged to carefully read and consider.

Pursuant to the Amended and Restated Certificate of Incorporation of GigCapital5, dated as of September 23, 2021 and as amended on September 23, 2022 and further amended on March 28, 2023 (the “Existing Charter”), we are providing our public stockholders with the right to demand that GigCapital5 redeem (the “Redemption Rights”), upon the Closing, shares of GigCapital5 Common Stock then held by them for cash equal to their pro rata share of the aggregate amount on deposit in the trust account (the “Trust Account”), calculated as of two business days prior to the consummation of the Merger (including interest earned on the funds held in the Trust Account and not previously released to GigCapital5 to pay its taxes). For illustrative purposes, based on the balance of the Trust Account of $[●] as of [●], 2023, the estimated per share redemption price would have been approximately $[●]. Public stockholders may elect to redeem their shares even if they vote for the Business Combination Proposal. A holder of shares of GigCapital5 Common Stock, together with any affiliate of the holder or any other person with whom the holder is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Securities Exchange Act of 1934, as amended), will be restricted from seeking Redemption Rights with respect to more than 15% of the aggregate number of shares of GigCapital5 Common Stock outstanding without the consent of GigCapital5. Accordingly, all shares of GigCapital5 Common Stock in excess of 15% held by a holder of shares of GigCapital5 Common Stock, together with any affiliate of such holder or any other person with whom such holder is acting in concert or as a “group,” will not be redeemed for cash without the consent of GigCapital5. We have no specified maximum redemption threshold under our Existing Charter, other than the aforementioned 15% threshold. Each redemption of shares of GigCapital5 Common Stock by our Public Stockholders will reduce the amount in the Trust Account.

After giving effect to the proposed Business Combination (assuming no Public Shares of GigCapital5 have been redeemed and no GigCapital5 Warrants have been exercised), we expect that there will be approximately 27,083,497 shares of the Combined Company Common Stock consisting of (i) 14,919,496 shares issued in the aggregate to holders of QT Imaging securities (after giving effect to the net exercise or conversion of (A) the In-the-Money Company Warrants that are not Assumed Warrants and (B) the Converting Notes) and as the Aggregate Excess QT Imaging Transaction Shares (ii) 3,019,001 shares held by GigCapital5’s Public Stockholders, (iii) 15,000 shares in the aggregate held by GigCapital5’s Treasurer and Chief Financial Officer, Brad Weightman, and Interest Solutions, LLC, an affiliate of ICR, LLC, an investor relations firm providing services to GigCapital5 (“ICR”), [and] (iv) 6,530,000 shares held by the Sponsor [and (ii) up to 2,600,000 shares held by PIPE Investors pursuant to PIPE Subscription Agreements.]

Pursuant to the terms of the Existing Charter, in no event will we redeem shares of GigCapital5 Common Stock in an amount that would result in our failure to have net tangible assets of at least $5,000,001 after giving effect to the redemptions of shares of GigCapital5 Common Stock by the public stockholders, including as of the time either immediately prior to or upon the Closing.

We are providing the accompanying proxy statement/prospectus and accompanying proxy card to our stockholders in connection with the solicitation of proxies to be voted at the Stockholders’ Meeting (including following any adjournments or postponements of the Stockholders’ Meeting). Information about the Stockholders’ Meeting, the proposed Business Combination and other related business to be considered by our stockholders at the Stockholders’ Meeting is included in this proxy statement/prospectus. Whether or not you plan to attend the Stockholders’ Meeting via the virtual meeting platform, we urge all our stockholders to read this proxy statement/prospectus, including the annexes and the accompanying financial statements of GigCapital5 and QT Imaging, carefully and in their entirety. In particular, we urge you to read carefully the section entitled “Risk Factors” beginning on page 64 of the attached proxy statement/prospectus.

After careful consideration, GigCapital5’s board of directors (the “GigCapital5 Board”) has determined that the Business Combination Proposal, the Board Classification Charter Proposal, the Additional Charter Amendments in Connection with the Business Combination Proposal, the Director Election Proposal, the Nasdaq Proposal, the Equity Incentive Plan Proposal, and the Adjournment Proposal (each as defined in the accompanying proxy statement/prospectus) are fair to and in the best interests of GigCapital5 and its stockholders and unanimously recommends that you vote or give instruction to vote “FOR” the Business Combination Proposal, “FOR” the Board Classification Charter Proposal, “FOR” the Additional Charter Amendments in Connection with the Business

Combination Proposal, “FOR” the Director Election Proposal, “FOR” the Nasdaq Proposal, “FOR” the Equity Incentive Plan Proposal, and “FOR” the Adjournment Proposal, if presented at the Stockholders’ Meeting.

The approval of each of the Business Combination Proposal, the Nasdaq Proposal, the Equity Incentive Plan Proposal, and the Adjournment Proposal, if presented, requires the affirmative vote (in person or by proxy) of the holders of a majority of the shares of GigCapital5 Common Stock entitled to vote thereon and actually cast at the Stockholders’ Meeting, voting as a single class. In addition, in accordance with the Business Combination Agreement, the parties to the Business Combination Agreement are also requiring the affirmative vote of holders of a majority of the shares of GigCapital5 Common Stock then outstanding, voting together as a single class, for the approval of the Board Classification Charter Proposal and the Additional Charter Amendments in Connection with the Business Combination Proposal. The approval of the Director Election Proposal requires the affirmative vote (in person or by proxy) of the holders of a plurality of the outstanding shares of GigCapital5 Common Stock entitled to vote thereon and actually cast at the Stockholders’ Meeting.

As of [●], 2023, the record date for the Stockholders’ Meeting (the “Record Date”), the Sponsor was entitled to vote an aggregate of 6,530,000 shares of GigCapital5 Common Stock. Such shares currently constitute approximately 68.3% of the outstanding shares of GigCapital5 Common Stock. The Sponsor has agreed to vote its shares of GigCapital5 Common Stock in favor of each of the proposals presented at the Stockholders’ Meeting. The Sponsor, GigCapital5 independent directors and certain of the Supporting QT Imaging Stockholders (as defined in the accompanying proxy statement/prospectus) and other stockholders of QT Imaging have, subject to limited exceptions, agreed to a lock-up following the Closing on their respective shares of Combined Company Common Stock which they already hold or will receive, pursuant to which such parties will not transfer shares of Combined Company Common Stock held by such parties for 180 days following the Closing subject to certain exceptions. The Sponsor has also agreed to a lock-up on the shares of stock that are a constituent part of its Private Placement Units, pursuant to which the Sponsor will not transfer such shares of stock for 180 days following the Closing subject to certain exceptions.

Your vote is very important. Whether or not you plan to attend the Stockholders’ Meeting, please vote as soon as possible by following the instructions in this proxy statement/prospectus to make sure that your shares are represented at the Stockholders’ Meeting. If you hold your shares in “street name” through a bank, broker or other nominee, you will need to follow the instructions provided to you by your bank, broker or other nominee to ensure that your shares are represented and voted at the Stockholders’ Meeting. Unless waived by the parties to the Business Combination Agreement, consummation of the proposed Business Combination is conditioned on the approval of the Business Combination Proposal, the Board Classification Charter Proposal, the Additional Charter Amendments in Connection with the Business Combination Proposal, the Director Election Proposal, the Nasdaq Proposal, and the Equity Incentive Plan Proposal at the Stockholders’ Meeting, subject to the terms of the Business Combination Agreement. If the Business Combination Proposal is not approved, the other proposals (except the Adjournment Proposal) will not be presented to the stockholders for a vote. If we fail to obtain the requisite stockholder approval for any of the Business Combination Proposal, the Board Classification Charter Proposal, the Additional Charter Amendments in Connection with the Business Combination Proposal, the Director Election Proposal, the Nasdaq Proposal, and the Equity Incentive Plan Proposal at the Stockholders’ Meeting, we will not satisfy the conditions to Closing set forth in the Business Combination Agreement and we may be prevented from closing the proposed Business Combination. The proposed Business Combination is not conditioned on approval of the Adjournment Proposal.

If you sign, date, and return your proxy card without indicating how you wish to vote, your proxy will be voted “FOR” each of the Proposals presented at the Stockholders’ Meeting. If you fail to return your proxy card or fail to instruct your bank, broker or other nominee how to vote, and do not attend the Stockholders’ Meeting in person via the virtual meeting platform, the effect will be that your shares will not be counted for purposes of determining whether a quorum is present at the Stockholders’ Meeting. If you are a stockholder of record and you attend the Stockholders’ Meeting and wish to vote in person via the virtual meeting platform, you may withdraw your proxy and vote in person via the virtual meeting platform.

TO EXERCISE YOUR REDEMPTION RIGHTS, YOU MUST DEMAND THAT GIGCAPITAL5 REDEEM YOUR SHARES FOR A PRO RATA PORTION OF THE FUNDS HELD IN THE TRUST

ACCOUNT AND TENDER YOUR SHARES TO GIGCAPITAL5’S TRANSFER AGENT AT LEAST TWO BUSINESS DAYS PRIOR TO THE VOTE AT THE STOCKHOLDERS’ MEETING. YOU MAY TENDER YOUR SHARES BY EITHER DELIVERING YOUR SHARE CERTIFICATE TO THE TRANSFER AGENT OR BY DELIVERING YOUR SHARES ELECTRONICALLY USING THE CONTINENTAL STOCK TRANSFER & TRUST COMPANY’S DWAC (DEPOSIT AND WITHDRAWAL AT CUSTODIAN) SYSTEM. IF THE PROPOSED BUSINESS COMBINATION IS NOT COMPLETED, THEN ANY SHARES YOU TENDERED FOR REDEMPTION WILL NOT BE REDEEMED FOR CASH. IF YOU HOLD THE SHARES IN STREET NAME, YOU WILL NEED TO INSTRUCT THE ACCOUNT EXECUTIVE AT YOUR BANK OR BROKER TO WITHDRAW THE SHARES FROM YOUR ACCOUNT IN ORDER TO EXERCISE YOUR REDEMPTION RIGHTS.

On behalf of our board of directors, I would like to thank you for your support of GigCapital5 and look forward to a successful completion of the proposed Business Combination.

Sincerely,

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES REGULATORY AGENCY HAS APPROVED OR DISAPPROVED THE TRANSACTIONS DESCRIBED IN THIS PROXY STATEMENT/PROSPECTUS, PASSED UPON THE MERITS OR FAIRNESS OF THE PROPOSED BUSINESS COMBINATION OR RELATED TRANSACTIONS OR PASSED UPON THE ADEQUACY OR ACCURACY OF THE DISCLOSURE IN THIS PROXY STATEMENT/PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY CONSTITUTES A CRIMINAL OFFENSE.

This proxy statement/prospectus is dated [●], 2023, and is expected to be first mailed or otherwise delivered to GigCapital5 stockholders on or about [●], 2023.

GIGCAPITAL5, INC.

1731 Embarcadero Rd., Suite 200, Palo Alto, California, 94303

NOTICE OF 2023 ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON [●], 2023

TO THE STOCKHOLDERS OF GIGCAPITAL5, INC.:

NOTICE IS HEREBY GIVEN that the 2023 annual meeting of the stockholders of GigCapital5, Inc., a Delaware corporation (“GigCapital5”), will be held at [●] Eastern Time, on [●], 2023, in virtual format (the “Stockholders’ Meeting”). You are cordially invited to attend the Stockholders’ Meeting, which will be held for the following purposes:

(1)    The Business Combination Proposal-To consider and vote upon a proposal to approve the Business Combination Agreement, dated as of December 8, 2022 (the “Business Combination Agreement”), by and among GigCapital5, QTI Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of GigCapital5 (“Merger Sub”), and QT Imaging, Inc., a Delaware corporation (“QT Imaging”), and the transactions contemplated thereby, pursuant to which Merger Sub will merge with and into QT Imaging, with QT Imaging surviving the merger as a wholly owned subsidiary of GigCapital5 (the “Merger” and, together with the other transactions contemplated by the Business Combination Agreement and any other agreement executed and delivered in connection with the Business Combination Agreement, the “Business Combination”). Following the closing of the Merger (the “Closing”), GigCapital5, which will be renamed “QT Imaging Holdings, Inc.” will be referred to as the “Combined Company.” A copy of the Business Combination Agreement is attached to this proxy statement/ prospectus as Annex A (the “Business Combination Proposal”);

(2)    The Board Classification Charter Proposal-To provide for the classification of our board of directors into three classes of directors with staggered terms of office and to make certain related changes;

(3)    The Additional Charter Amendments in Connection with the Business Combination Proposal-To consider and vote upon two proposals to adopt the proposed Second Amended and Restated Certificate of Incorporation of GigCapital5 (the “Proposed Charter”), in the form attached hereto as Annex B (the “Additional Charter Amendments in Connection with the Business Combination Proposal”);

(4)    The Director Election Proposal-To consider and vote upon a proposal to elect seven directors to serve on the board of directors of the Combined Company (the “Combined Company Board”) until the first annual meeting of stockholders following the effectiveness of the Proposed Charter, in the case of Class I directors; the second annual meeting of stockholders following the effectiveness of the Proposed Charter, in the case of Class II directors; and the third annual meeting of stockholders following the effectiveness of the Proposed Charter, in the case of Class III directors; and, in each case, until their respective successors are duly elected and qualified (the “Director Election Proposal”);

(5)     The Nasdaq Proposal-To consider and vote upon a proposal to approve, for purposes of complying with applicable listing rules of the Nasdaq: (i) the issuance of shares of GigCapital5 Common Stock to QT Imaging stockholders pursuant to the Business Combination Agreement[; and (ii) the issuance of up to 2,600,000 shares of GigCapital5 Common Stock to PIPE Investors pursuant to PIPE Subscription Agreements] (the “Nasdaq Proposal”);

(6)     The Equity Incentive Plan Proposal-To consider and vote upon a proposal to approve and adopt the QT Imaging Holdings, Inc. 2023 Equity Incentive Plan attached to this proxy statement/prospectus as Annex G (the “Equity Incentive Plan Proposal”);

(7)     The Adjournment Proposal-To consider and vote upon a proposal to approve the adjournment of the Stockholders’ Meeting to a later date or dates, if necessary, to permit further solicitation and vote of proxies in the event that there are insufficient votes for the approval of the Business Combination Proposal, the Board Classification Charter Proposal, the Additional Charter Amendments in Connection with the Business

Combination Proposal, the Director Election Proposal, the Nasdaq Proposal, or the Equity Incentive Plan Proposal (the “Adjournment Proposal” and, together with the Business Combination Proposal, the Board Classification Charter Proposal, the Additional Charter Amendments in Connection with the Business Combination Proposal, the Director Election Proposal, the Nasdaq Proposal, and the Equity Incentive Plan Proposal, each, a “Proposal” and collectively, the “Proposals”).

These items of business are described in the attached proxy statement/prospectus, which we encourage you to read in its entirety before voting. Only holders of record of shares of GigCapital5 Common Stock at the close of business on [●], 2023, the record date for the Stockholders’ Meeting (the “Record Date”) are entitled to notice of the Stockholders’ Meeting and to vote and have their votes counted at the Stockholders’ Meeting and any adjournments or postponements of the Stockholders’ Meeting.

Pursuant to the Amended and Restated Certificate of Incorporation of GigCapital5, dated September 23, 2021 and as amended on September 23, 2022 and further amended on March 28, 2023 (the “Existing Charter”), GigCapital5 will provide holders of shares of GigCapital5 Common Stock with the opportunity to redeem such shares for cash equal to their pro rata share of the aggregate amount on deposit in the trust account established in connection with GigCapital5’s initial public offering (the “Trust Account”), calculated as of two business days prior to the consummation of the transactions contemplated by the Business Combination Proposal (including interest earned on the funds held in the Trust Account and not previously released to GigCapital5 to pay its taxes). For illustrative purposes, based on funds in the Trust Account of approximately $[●] on [●], 2023, the estimated per share redemption price would have been approximately $[●], excluding additional interest earned on the funds held in the Trust Account and not previously released to GigCapital5 to pay taxes. Holders of GigCapital5 Common Stock may elect to redeem their shares of GigCapital5 Common Stock even if they vote for the Business Combination Proposal. A holder of shares of GigCapital5 Common Stock, together with any affiliate of the holder or any other person with whom the holder is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”)), will be restricted from seeking Redemption Rights with respect to more than 15% of the aggregate number of shares of GigCapital5 Common Stock outstanding without the consent of GigCapital5. Accordingly, all shares of GigCapital5 Common Stock in excess of 15% held by a holder of shares of GigCapital5 Common Stock, together with any affiliate of such holder or any other person with whom such holder is acting in concert or as a “group,” will not be redeemed for cash without the consent of GigCapital5. Currently, GigAcquistions5, LLC, a Delaware limited liability company (the “Sponsor”) (in which certain of GigCapital5’s directors and officers are directly or indirectly members), owns approximately 68.3% of the outstanding shares of GigCapital5 Common Stock, consisting of shares of GigCapital5 Common Stock and units, purchased in a private placement, each unit consisting of one share of GigCapital5 Common Stock and one redeemable GigCapital5 warrant. The Sponsor has agreed to vote any shares of GigCapital5 Common Stock owned by it in favor of each of the Proposals presented at the Stockholders’ Meeting.

After careful consideration, GigCapital5’s board of directors (the “GigCapital5 Board”) has determined that the Business Combination Proposal, the Board Classification Charter Proposal, the Additional Charter Amendments in Connection with the Business Combination Proposal, the Director Election Proposal, the Nasdaq Proposal, the Equity Incentive Plan Proposal, and the Adjournment Proposal are fair to and in the best interests of GigCapital5 and its stockholders and unanimously recommends that you vote or give instruction to vote “FOR” the Business Combination Proposal, “FOR” the Board Classification Charter Proposal, “FOR” the Additional Charter Amendments in Connection with the Business Combination Proposal, “FOR” the Director Election Proposal, “FOR” the Nasdaq Proposal, “FOR” the Equity Incentive Plan Proposal, and “FOR” the Adjournment Proposal, if presented at the Stockholders’ Meeting.

The approval of each of the Business Combination Proposal, the Nasdaq Proposal, the Equity Incentive Plan Proposal, and the Adjournment Proposal, if presented, requires the affirmative vote (in person or by proxy) of the holders of a majority of the shares of GigCapital5 Common Stock entitled to vote thereon and actually cast at the Stockholders’ Meeting, voting as a single class. In addition, in accordance with the Business Combination Agreement, the parties to the Business Combination Agreement are also requiring the affirmative vote of holders of a majority of the shares of GigCapital5 Common Stock then outstanding, voting together as a single class, for

the approval of the Board Classification Charter Proposal and the Additional Charter Amendments in Connection with the Business Combination Proposal. The approval of the Director Election Proposal requires the affirmative vote (in person or by proxy) of the holders of a plurality of the outstanding shares of GigCapital5 Common Stock entitled to vote thereon and actually cast at the Stockholders’ Meeting.

Consummation of the proposed Business Combination is conditioned on the approval of the Business Combination Proposal, the Board Classification Charter Proposal, the Additional Charter Amendments in Connection with the Business Combination Proposal, the Director Election Proposal, the Nasdaq Proposal, and the Equity Incentive Plan Proposal at the Stockholders’ Meeting, subject to the terms of the Business Combination Agreement. The proposed Business Combination is not conditioned on the Adjournment Proposal. If the Business Combination Proposal is not approved, the other proposals (except the Adjournment Proposal) will not be presented to the stockholders for a vote. The proxy statement/prospectus accompanying this notice explains the Business Combination Agreement and the transactions contemplated thereby, as well as the Proposals to be considered at the Stockholders’ Meeting. Please review the proxy statement/prospectus carefully.

All GigCapital5 stockholders are cordially invited to attend the Stockholders’ Meeting in virtual format. GigCapital5 stockholders may attend, vote, and examine the list of GigCapital5 stockholders entitled to vote at the Stockholders’ Meeting by visiting https://www.[●] and entering the control number found on their proxy card, voting instruction form or notice included in their proxy materials. In light of public health concerns regarding the coronavirus (“COVID-19”) pandemic, the Stockholders’ Meeting will be held in virtual meeting format only. You will not be able to attend the Stockholders’ Meeting physically. To ensure your representation at the Stockholders’ Meeting, you are urged to complete, sign, date and return the enclosed proxy card as soon as possible. If your shares are held in an account at a brokerage firm or bank, you must instruct your broker or bank on how to vote your shares.

Your vote is important regardless of the number of shares you own. Whether you plan to attend the Stockholders’ Meeting or not, please sign, date, and return the enclosed proxy card as soon as possible in the envelope provided. If your shares are held in “street name” or are in a margin or similar account, you should contact your broker to ensure that votes related to the shares you beneficially own are properly counted.

If you have any questions or need assistance voting your shares, please call our proxy solicitor, Morrow Sodali LLC, toll free at (800) 662-5200.

Thank you for your participation. We look forward to your continued support.

[●], 2023

IF YOU RETURN YOUR PROXY CARD WITHOUT AN INDICATION OF HOW YOU WISH TO VOTE, YOUR SHARES WILL BE VOTED IN FAVOR OF EACH OF THE PROPOSALS. TO EXERCISE YOUR REDEMPTION RIGHTS, YOU MUST ELECT TO HAVE GIGCAPITAL5 REDEEM YOUR SHARES FOR A PRO RATA PORTION OF THE FUNDS HELD IN THE TRUST ACCOUNT AND TENDER YOUR SHARES TO GIGCAPITAL5’S TRANSFER AGENT AT LEAST TWO (2) BUSINESS DAYS PRIOR TO THE STOCKHOLDERS’ MEETING. YOU MAY TENDER YOUR SHARES BY EITHER DELIVERING YOUR SHARE CERTIFICATE TO THE TRANSFER AGENT OR BY DELIVERING YOUR SHARES ELECTRONICALLY USING THE CONTINENTAL STOCK TRANSFER & TRUST COMPANY’S DWAC (DEPOSIT AND WITHDRAWAL AT CUSTODIAN) SYSTEM. IF THE PROPOSED BUSINESS COMBINATION IS NOT COMPLETED, THEN ANY SHARES YOU TENDERED WILL NOT BE REDEEMED FOR CASH. IF YOU HOLD THE SHARES IN STREET NAME, YOU WILL NEED TO INSTRUCT THE ACCOUNT EXECUTIVE AT YOUR BANK OR BROKER TO WITHDRAW THE SHARES FROM YOUR ACCOUNT IN ORDER TO EXERCISE YOUR REDEMPTION RIGHTS. SEE “MEETING OF GIGCAPITAL5 STOCKHOLDERS-REDEMPTION RIGHTS” FOR MORE SPECIFIC INSTRUCTIONS.

TABLE OF CONTENTS

Annexes

A–Business Combination Agreement

B–GigCapital5 Second Amended and Restated Certificate of Incorporation

C–Sponsor Support Agreement

D–Stockholder Support Agreement

E–Form of Registration Rights Agreement

F–Form of Lock-Up Agreement

G–QT Imaging Holdings, Inc. 2023 Equity Incentive Plan

H–Form of the Amended and Restated Bylaws of QT Imaging Holdings, Inc.

ii

BASIS OF PRESENTATION AND GLOSSARY

As used in this proxy statement/prospectus, unless otherwise noted or the context otherwise requires, references to:

“Additional September 2022 Contributions” are to the amounts the Sponsor agreed to contribute as a non-interest bearing loan of $160,000 per month to GigCapital5 on a monthly basis commencing on September 28, 2022, and occurring on the 28th day of each subsequent month, up to March 28, 2023;

“Additional March 2023 Contributions” are to the amounts the Sponsor has agreed to contribute as a non-interest bearing loan of $100,000 per month to GigCapital5 on a monthly basis commencing on March 28, 2023, and occurring on the 28th day of each subsequent month, or portion thereof, up to September 28, 2023, that is needed by GigCapital5 to complete the proposed Business Combination no later than the Extended Date;

“Aggregate Closing Merger Consideration” are to a number of shares of GigCapital5 Common Stock equal to the difference of: (a) the quotient of (i) the Aggregate Closing Merger Consideration Value, divided by (ii) $10.00; minus (b) the Aggregate Excess QT Imaging Transaction Expenses Shares;

“Aggregate Closing Merger Consideration Value” are to (a) the sum of (i) $151,000,000, plus (ii) the sum of the exercise prices of all In-the-Money Company Warrants, plus (iii) the QT Imaging Closing Cash, plus (iv) the Paid QT Imaging Transaction Expenses, minus (b) the debt of QT Imaging as of immediately prior to the Effective Time after conversion of any Converting Notes, and which debt of QT Imaging will not exceed $4,000,000;

“Aggregate Excess QT Imaging Transaction Expenses Shares” are to a number of shares of GigCapital5 Common Stock equal to the quotient of (a) the amount of QT Imaging Transaction Expenses, in excess of $4,000,000, if any, divided by (b) $10.00, and rounded up to the nearest whole share, and will include all shares to be issued to two entities providing services to QT Imaging as partial payment of the QT Imaging Transaction Expenses for such entities;

“Ancillary Agreements” are to the Stockholder Support Agreement, the Sponsor Support Agreement, the Registration Rights Agreement, the Lock-Up Agreement, and all other agreements, certificates and instruments executed and delivered by GigCapital5, Merger Sub or QT Imaging in connection with the transactions and specifically contemplated by the Business Combination Agreement;

“Assumed Warrants” are to each In-the-Money Company Warrant outstanding as of immediately prior to the Effective Time and that is not exercised and exchanged prior to the Effective Time but is instead, without any action on the part of the holder thereof and in accordance with the provisions of such In-the-Money Company Warrant (for the avoidance of doubt, as may be amended following the date of the Business Combination Agreement with the written approval of GigCapital5), converted into a warrant to acquire a number of shares of GigCapital5 Common Stock at an adjusted exercise price per share;

“Available Cash” are to, as of immediately prior the Closing, an amount of cash equal to: (a) the sum of (i) the funds in the Trust Account following the exercise of any Redemption Rights by any Public Stockholders, plus (ii) cash available to GigCapital5 from any other sources, including the PIPE Investment Amounts, plus (iii) the QT Imaging Closing Cash, minus (b) (i) the QT Imaging Transaction Expenses that are not Paid QT Imaging Transaction Expenses (other than any such QT Imaging Transaction Expenses to be satisfied by the issuance of shares of GigCapital5 Common Stock, including the Aggregate Excess QT Imaging Transaction Expenses Shares) and (ii) Unpaid GigCapital5 Transaction Expenses (other than any such Unpaid GigCapital5 Transaction Expenses to be satisfied by the issuance of shares of GigCapital5 Common Stock to the extent that the aggregate amount of such expenses exceeds $7,000,000);

“Bridge Financing” are to a financing of QT Imaging on terms and conditions previously approved in writing by GigCapital5, pursuant to which QT Imaging may (a) obtain financing in an aggregate principal amount not to exceed $4,000,000, and (b) issue to the investors QT Imaging Warrants to purchase 1,000,000

1

shares of QT Imaging Common Stock for an exercise price of $4.00 per share, and which QT Imaging Warrants, to the extent outstanding immediately prior to the Effective Time, shall be subject to the provisions of the Business Combination Agreement as In-the-Money Company Warrants;

“Business Combination” are to the Merger and the other transactions contemplated by the Transaction Documents;

“Business Combination Agreement” are to that certain Business Combination Agreement entered into on December 8, 2022, by and among GigCapital5, Inc., a Delaware corporation (“GigCapital5”), QTI Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of GigCapital5 (“Merger Sub”), and QT Imaging, Inc., a Delaware corporation (“QT Imaging”) , pursuant to which Merger Sub will merge with and into QT Imaging, with QT Imaging surviving the merger as a wholly owned subsidiary of GigCapital5 (the “Merger”);

“Closing” are to the closing of the transactions contemplated by the Business Combination Agreement;

“Code” are to the Internal Revenue Code of 1986, as amended;

“Combined Company” are to GigCapital5, which will be renamed “QT Imaging Holdings, Inc.”, following the proposed Business Combination and the other transactions contemplated by the Business Combination Agreement;

“Combined Company Board” are to the board of directors of the Combined Company;

“Combined Company Common Stock” are to shares of GigCapital5 Common Stock following the Closing;

“Combined Company Option” are to each option to purchase shares of Combined Company Common Stock following the Closing;

“Completion Window” are to the period that expires on the Extended Date, or such later date as the stockholders may approve an extension for GigCapital5 to complete its initial business combination;

“Converting Notes” are to the QT Imaging Convertible Notes that are being converted into shares of QT Imaging Common Stock immediately prior to the Effective Time in accordance with the terms of such QT Imaging Convertible Notes;

“DGCL” are to the Delaware General Corporation Law, as may be amended from time to time;

“Effective Time” are to such a time when the merger certificate has been accepted for filing by the Secretary of State of the State of Delaware, or at such later time as may be agreed by GigCapital5 and QT Imaging in writing and specified in the merger certificate;

“Equity Incentive Plan” are to the QT Imaging Holdings, Inc. 2023 Equity Incentive Plan in the form attached hereto as Annex G;

“Exchange Act” are to the Securities Exchange Act of 1934, as amended;

“Exchange Ratio” are to the quotient of (a) the Aggregate Closing Merger Consideration divided by (b) the QT Imaging Fully Diluted Capital Stock;

“Existing Charter” are to the Amended and Restated Certificate of Incorporation of GigCapital5, dated as of September 23, 2021 and as amended on September 23, 2022 and further amended on March 28, 2023;

“Extended Date” are to September 28, 2023;

“First Extension Amendment” are to the amendment to the Existing Charter approved by GigCapital5’s stockholders on September 23, 2022 to extend the date by which GigCapital5 must consummate a business

2

combination transaction from September 28, 2022 (the date which is 12 months from the closing date of GigCapital5’s initial public offering of units) on a monthly basis up to the March 28, 2023;

“Founder Shares” are to 5,735,000 remaining shares of GigCapital5 Common Stock initially purchased by the Sponsor in a private placement prior to the GigCapital5 IPO following the forfeiture of 4,312,500 shares;

“GAAP” are to accounting principles generally accepted in the United States, as applied on a consistent basis;

“GigCapital5 Common Stock” are to shares of common stock, par value $0.0001 per share, of GigCapital5 prior to the Closing;

“GigCapital5 Board” are to the board of directors of GigCapital5 prior to the Closing;

“GigCapital5 Board Recommendation” is a recommendation of the GigCapital5 Board to the GigCapital5 stockholders that such stockholders approve the proposals included herein;

“GigCapital5 IPO” are to the initial public offering by GigCapital5, which closed on September 28, 2021;

“GigCapital5 Units” are to the public units, comprised on one share of GigCapital5 Common Stock and one redeemable GigCapital5 Warrant, issued at the closing of the GigCapital5 IPO;

“GigCapital5 Warrants” are to all outstanding warrants of GigCapital5, each whole warrant of which entitles the holder to purchase one share of GigCapital5 Common Stock at an exercise price of $11.50 per share;

“In-the-Money Company Warrants” are to (a) the Pre-Signing In-the-Money Company Warrants and (b) any additional QT Imaging Warrants issued pursuant to the Bridge Financing;

“In-the-Money Company Warrant Shares” are to the aggregate number of shares of QT Imaging Common Stock issuable upon full exercise, exchange or conversion of all In-the-Money Company Warrants outstanding as of immediately prior to the Effective Time and that will become an Assumed Warrant;

“Investment Company Act” are to the Investment Company Act of 1940, as amended;

“Key QT Imaging Stockholders” are to those certain stockholders of QT Imaging who are parties to the Stockholder Support Agreement;

“Lock-Up Agreement” are to that certain Lock-Up Agreement to be entered into by and between GigCapital5 and certain stockholders of QT Imaging;

“March 2023 Partial Redemption” are to the Public Stockholders’ election in March 2023 to redeem 995,049 shares at $10.50 per share for total redemption proceeds of approximately $10,449,626;

“Nasdaq” are to The Nasdaq Global Market;

“Outside Date” are to September 8, 2023, which is nine months after the date the GigCapital5 and QT Imaging executed the Business Combination Agreement;

“Paid QT Imaging Transaction Expenses” are all QT Imaging Transaction Expenses that QT Imaging will have paid prior to the close of business on the business day immediately preceding the Closing;

“PCAOB Financial Statements” are to (i) the audited consolidated financial statements of QT Imaging and its subsidiaries for the years ended December 31, 2021 and 2022, and (ii) the condensed consolidated reviewed financial statements of QT Imaging and its subsidiaries for the nine month periods ended September 30, 2022 and 2021, in accordance with the auditing standards of the Public Company Accounting Oversight Board (United States);

3

“Per Share Merger Consideration” are to the right of each issued and outstanding share of QT Imaging Common Stock (including shares issued upon the exercise or conversion of QT Imaging Options, QT Imaging Warrants and QT Imaging Convertible Notes, but excluding each share of QT Imaging Common Stock held in the treasury of QT Imaging which will be cancelled without any conversion of such shares of QT Imaging Common Stock held in the treasury and dissenting shares) to receive a number of shares of GigCapital5 Common Stock equal to the Exchange Ratio;

“PIPE Investment” are to the potential purchase of an aggregate of up to [2,600,000] shares of GigCapital5 Common Stock pursuant to the PIPE Subscription Agreements;

“PIPE Investors” are to the investors who subscribe for the purchase of GigCapital5 Common Stock, convertible promissory notes or other securities or any combination of such securities to be subscribed for pursuant to the terms of one or more PIPE Subscription Agreements;

“PIPE Subscription Agreements” are to the subscription agreements for the PIPE Investment on terms and conditions mutually agreeable to GigCapital5 and QT Imaging (such agreement not to be unreasonably withheld, conditioned or delayed), provided that, unless otherwise agreed to, the aggregate gross proceeds under the PIPE Subscription Agreements will not exceed $26,000,000;

“Pre-Signing In-the-Money Company Warrants” are to each QT Imaging Warrant disclosed by QT Imaging to GigCapital5 concurrent with the entry into the Business Combination Agreement that, to the extent such QT Imaging Warrant remains outstanding immediately prior to the Closing, would constitute an “in-the-money” QT Imaging Warrant with respect to the transactions contemplated by the Business Combination Agreement;

“Private Placement Warrants” are to the warrants sold as part of the Private Placement Units.

“Private Placement Units” are to 795,000 units sold to the Sponsor in a private placement simultaneously with the GigCapital5 IPO;

“Public Shares” are to shares of GigCapital5 Common Stock sold as part of the GigCapital5 Units (whether they were purchased in the GigCapital5 IPO or thereafter in the open market);

“Public Stockholders” are to the holders of Public Shares, including the Sponsor and GigCapital5’s management team to the extent the Sponsor and/or members of GigCapital5’s management team purchase Public Shares in the open market, provided that the Sponsor’s and each member of GigCapital5’s management team’s status as a “Public Stockholder” will only exist with respect to such Public Shares;

“QT Imaging Board” are to the board of directors of QT Imaging;

“QT Imaging Closing Cash” are to the cash of QT Imaging as of immediately prior to the Effective Time;

“QT Imaging Common Stock” are to the shares of common stock, par value $0.001 per share, of QT Imaging;

“QT Imaging Convertible Notes” are to the convertible notes of QT Imaging;

“QT Imaging Convertible Notes Shares” are to the shares issued pursuant to the conversion of the Converting Notes;

“QT Imaging Equity Securities” are to the In-the-Money Company Warrant Shares, the QT Imaging Common Stock, the In-the-Money Company Warrants and the QT Imaging Convertible Notes Shares;

“QT Imaging Fully Diluted Capital Stock” are to, without duplication, the sum of (a) the aggregate number of shares of QT Imaging Common Stock that are issued and outstanding as of immediately prior to the Effective

4

Time (including shares issued upon the exercise of QT Imaging Options, the shares issued upon exercise of QT Imaging Warrants, and the QT Imaging Convertible Notes Shares, in each case immediately prior to the Effective Time, but excluding each share of QT Imaging Common Stock held in the treasury of QT Imaging which will be cancelled without any conversion of such shares of QT Imaging Common Stock held in the treasury), and (b) the aggregate number of In-the-Money Company Warrant Shares;

“QT Imaging Option” are to each option to purchase shares of QT Imaging Common Stock that is outstanding at the Effective Time;

“QT Imaging Option Plan” are to the QT Imaging, Inc. 2021 Stock Incentive Plan, as such may have been amended, supplemented or modified from time to time;

“QT Imaging stockholders” are to the stockholders of QT Imaging prior to the Closing;

“QT Imaging Transaction Expenses” are to the amount of transaction expenses of QT Imaging incurred by or on its behalf in connection with the preparation, negotiation and execution of the Business Combination Agreement and the consummation of the transactions that the Business Combination Agreement contemplates;

“QT Imaging Warrant” are to each warrant to purchase shares of QT Imaging Common Stock;

“Record Date” are to [●], 2023, the record date for the Stockholders’ Meeting;

“Redemption Rights” are to the right to demand that GigCapital5 redeem such shares for a pro rata portion of the cash held in the Trust Account, calculated as of two business days prior to the Closing (including interest earned on the funds held in the Trust Account and not previously released to GigCapital5 to pay taxes) upon the Closing;

“Registrant” are to GigCapital5, Inc., a Delaware corporation;

“Registration Rights Agreement” are to that certain Registration Rights Agreement to be entered into by and between GigCapital5 and certain stockholders of QT Imaging;

“Representative” are to William Blair & Company L.L.C. (“William Blair”) and Wells Fargo Securities LLC (“Wells Fargo”), the GigCapital5 IPO underwriters, and certain of their employees;

“SEC” are to the U.S. Securities and Exchange Commission;

“Second Extension Amendment” are to the amendment to the Existing Charter approved by GigCapital5’s stockholders on March 28, 2023 to extend the date by which GigCapital5 must consummate a business combination transaction from March 28, 2023 (the date which is 18 months from the closing date of GigCapital5’s initial public offering of units) on a monthly basis up to the September 28, 2023;

“Securities Act” are to the Securities Act of 1933, as amended;

“September 2022 Partial Redemption” are to the Public Stockholders’ election in September 2022 to redeem 18,985,950 shares at $10.12 per share for total redemption proceeds of approximately $193,138,312;

“Sponsor” are to GigAcquisitions5, LLC, a Delaware limited liability company;

“Sponsor Support Agreement” are to that certain Sponsor Support Agreement to be entered into by and between the Sponsor, GigCapital5 and QT Imaging;

“Stockholders’ Meeting” are to the 2023 annual meeting of the stockholders of GigCapital5;

5

“Stockholder Support Agreement” are to that certain Stockholder Support Agreement to be entered into by and between GigCapital5 and certain stockholders of QT Imaging;

“Supporting QT Imaging Stockholders” are to certain stockholders of QT Imaging who, in the aggregate, hold at least a majority of the outstanding shares of QT Imaging Common Stock;

“Transaction Documents” are to the Business Combination Agreement and any other agreement executed and delivered in connection therewith;

“Trust Account” are to the trust account established by GigCapital5 in connection with the GigCapital5 IPO for the benefit of its stockholders at J.P. Morgan Chase Bank, N.A.;

“Unpaid GigCapital5 Transaction Expenses” are to the amount of transaction expenses of GigCapital5 or Merger Sub incurred by or on its behalf in connection with the preparation, negotiation and execution of the Business Combination Agreement and the consummation of the transactions that the Business Combination Agreement contemplates to be paid at the Closing and costs and expenses payable to the provider of a buyer-side representation and warranty insurance policy to be obtained by GigCapital5, each of which have not been paid as of the Closing;

“VWAP” are to, for any security as of any date(s), the dollar volume-weighted average price for such security on the principal securities exchange or securities market on which such security is then traded during the period beginning at 9:30:01 a.m., New York time, and ending at 4:00:00 p.m., New York time, as reported by Bloomberg through its “HP” function (set to weighted average) or, if the foregoing does not apply, the dollar volume-weighted average price of such security in the over-the-counter market on the electronic bulletin board for such security during the period beginning at 9:30:01 a.m., New York time, and ending at 4:00:00 p.m., New York time, as reported by Bloomberg, or, if no dollar volume-weighted average price is reported for such security by Bloomberg for such hours, the average of the highest closing bid price and the lowest closing ask price of any of the market makers for such security as reported by OTC Markets Group Inc. If the VWAP cannot be calculated for such security on such date(s) on any of the foregoing bases, the VWAP of such security on such date(s) will be the fair market value per share on such date(s) as reasonably determined in good faith by a majority of the disinterested independent directors of the Combined Company Board at such time; and

“Warrants” are to GigCapital5 Warrants sold as part of the GigCapital5 Units (whether they were purchased in the GigCapital5 IPO or thereafter in the open market).

Unless specified otherwise, amounts in this proxy statement/prospectus are presented in United States (“U.S.”) dollars.

Defined terms in the financial statements contained in this proxy statement/prospectus have the meanings ascribed to them in the financial statements.

6

TRADEMARKS, TRADE NAMES AND SERVICE MARKS

GigCapital5 and QT Imaging own or have rights to trademarks, trade names and service marks that they use in connection with the operation of their business. In addition, their names, logos and website names and addresses are their trademarks or service marks. Other trademarks, trade names and service marks appearing in this proxy statement/prospectus are the property of their respective owners. Solely for convenience, in some cases, the trademarks, trade names and service marks referred to in this proxy statement/ prospectus, including logos, artwork and other visual displays, may appear without the applicable ®, TM and SM symbols, but GigCapital5 and QT Imaging will assert, to the fullest extent under applicable law, their rights to these trademarks, trade names and service marks. GigCapital5 and QT Imaging do not intend the use or display of other entities’ trade names, trademarks, or service marks to imply a relationship with, or endorsement or sponsorship of, any other entity.

7

QUESTIONS AND ANSWERS

The questions and answers below highlight only selected information from this proxy statement/prospectus and only briefly address some commonly asked questions about the proposed Business Combination, the Stockholders’ Meeting, and the Proposals (as defined herein) to be presented at the Stockholders’ Meeting. The following questions and answers do not include all the information that is important to GigCapital5 stockholders. You are urged to carefully read this entire proxy statement/prospectus, including the annexes and the other documents referred to herein, to fully understand the proposed Business Combination and the voting procedures for the Stockholders’ Meeting.

QUESTIONS AND ANSWERS ABOUT THE PROPOSED BUSINESS COMBINATION

GigCapital5 will hold the Stockholders’ Meeting to, among other things, obtain the approvals required for the proposed Business Combination, and you are receiving this proxy statement/prospectus in connection with such meeting. See “The Business Combination Agreement.” In addition, a copy of the Business Combination Agreement is attached to this proxy statement/prospectus as Annex A. We urge you to carefully read this proxy statement/prospectus, including the annexes and the other documents referred to herein, in their entirety.

8

In addition, at the Effective Time:

The merger consideration will be issued to holders of QT Imaging Equity Securities in accordance with the terms of the Business Combination Agreement. In addition, pursuant to the terms of the Business Combination Agreement, shares of Combined Company Common Stock will be issued to such other parties entitled pursuant to agreements with QT Imaging to receive shares of the Combined Company Common Stock as partial payment for compensation at the Closing. The portion of the merger consideration issuable to any person by virtue of the Merger will be calculated on an aggregate basis with respect to all shares of capital stock of QT Imaging held of record by such person immediately prior to the Effective Time, and after such aggregation, any fractional share of GigCapital5 Common Stock that would otherwise be issuable to such person following such aggregation will be rounded up to a whole share of GigCapital5 Common Stock.

9

10

GigCapital5 is, and after the Closing will continue to be, managed by its board of directors. Following the closing, the size of our board of directors will increase to seven directors and will consist of Dr. Avi S. Katz, Dr. Raluca Dinu, Dorothy D. Hayes, Dr John Klock, Dan Dickson, Gerald McMorrow and [●]. Following the Closing, we expect that a majority of the directors will be independent under applicable Nasdaq listing rules. Other than Dr. Katz, Dr. Dinu, and Ms. Hayes, there are no existing officers or directors of GigCapital5 who will hold any post-combination employment or directorships with, or receive any benefits from, the Combined Company, and there have been no discussions of anyone doing so. See “Management of the Combined Company Following the Business Combination.”

The table below shows the relative ownership levels of holders of Combined Company Common Stock following the proposed Business Combination under varying redemption scenarios (after giving effect to the September 2022 Partial Redemption and the March 2023 Partial Redemption).

11

The table below presents possible sources of dilution and the extent of such dilution that non-redeeming public stockholders could experience in connection with the Closing across a range of varying redemption scenarios (after giving effect to the September 2022 Partial Redemption and the March 2023 Partial Redemption). In an effort to illustrate the extent of such dilution, the table below assumes (i) the exercise of all 23,000,000 Warrants and 795,000 warrants that are part of the Private Placement Units, (ii) the exercise of the Assumed Warrants, and (iii) the full issuance and exercise of shares under the Equity Incentive Plan that would be issuable upon the Closing.

For more information, see “Unaudited Pro Forma Condensed Combined Financial Information.”

Furthermore, assuming no further redemptions (after giving effect to the September 2022 Partial Redemption and the March 2023 Partial Redemption), the pro forma amount of cash per share of GigCapital5 Common Stock, which we calculate as the amount of Available Cash divided by (a) the number of shares of GigCapital5 Common Stock outstanding immediately prior to the Closing less (b) any Public Shares for which Redemption Rights have been exercised (but without giving effect to the exercise of any warrants), is $[●] per share. Assuming maximum redemptions, the pro forma amount of cash per share of GigCapital5 Common Stock would be $[●] per share.

12

See “Risk Factors — One of the Representatives, Wells Fargo, without any consideration from GigCapital5 or QT Imaging, waived its entitlement to deferred underwriting fees and disclaimed any responsibility for the proposed Business Combination, but would be entitled to such compensation in connection with an alternative business combination, should the proposed Business Combination be terminated, and remains entitled to customary indemnification and contribution obligations of GigCapital5 in connection with the Business Combination” for additional information.

13

QUESTIONS AND ANSWERS ABOUT THE STOCKHOLDERS’ MEETING

GigCapital5 will hold the Stockholders’ Meeting to consider and vote upon these proposals (collectively, the “Proposals”). This proxy statement/prospectus contains important information about the proposed Merger and the other matters to be acted upon at the Stockholders’ Meeting.

Stockholders should read this proxy statement/prospectus carefully, including the annexes and the other documents referred to herein.

Pursuant to the Business Combination Agreement, consummation of the proposed Business Combination is conditioned on the approval of each of the Business Combination Proposal, the Board Classification Charter

14

Proposal, the Additional Charter Amendments in Connection with the Business Combination Proposal, the Nasdaq Proposal, and the Equity Incentive Plan Proposal. If the Business Combination Proposal is not approved, the other proposals, except the Adjournment Proposal, will not be presented to stockholders for a vote.

The vote of stockholders is important. Stockholders are encouraged to vote as soon as possible after carefully reviewing this proxy statement/prospectus.

Based on its due diligence investigations of QT Imaging and the industry in which it operates, including the financial and other information provided by QT Imaging in the course of their negotiations in connection with the Business Combination Agreement, GigCapital5 believes that consummating the Merger is advisable and in the best interests of GigCapital5 and its stockholders. See “Meeting of GigCapital5’s Stockholders-Recommendation of GigCapital5 Board of Directors” and “Background of the Business Combination-The GigCapital5 Board’s Reasons for Approval of the Business Combination.”

15

16

These factors are discussed in greater detail in the section entitled “Background of the Business Combination—The GigCapital5 Board’s Reasons for the Approval of the Business Combination” as well as in the section entitled “Risk Factors—Risks Related to the Business Combination.”

Notwithstanding the foregoing, a holder of Public Shares, together with any affiliate of such holder or any other person with whom such holder is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Exchange Act) will be restricted from seeking redemption with respect to more than 15% of the total then outstanding Public Shares without the consent of GigCapital5. Accordingly, all Public Shares in excess of 15% held by a Public Stockholder, together with any affiliate of such stockholder or any other person with whom such holder is acting in concert or as a “group,” will not be redeemed without the consent of GigCapital5.

Under GigCapital5’s Existing Charter, the Public Shares can only be redeemed if GigCapital5 has at least $5,000,001 of net tangible assets remaining, including at the time either immediately prior to or upon the Closing.

The holders of the Warrants do not have Redemption Rights with respect to the Warrants. However, pursuant to and in accordance with the Warrant Agreement, GigCapital5 may redeem the Warrants following the Closing under certain circumstances. See “Questions and Answers - How do the Public Warrants Differ from the Private Placement Warrants and What are the Related Risks for any Public Warrant Holders Post Business Combination?”

17

Any request for redemption, once made by a holder of Public Shares, may be withdrawn at any time up to the time the vote is taken with respect to the Business Combination Proposal at the Stockholders’ Meeting. If you deliver your shares for redemption to GigCapital5’s transfer agent and later decide prior to the Stockholders’ Meeting not to elect redemption, you may request that GigCapital5’s transfer agent return the shares (physically or electronically). If a holder of Public Shares properly makes a request for redemption and the Public Shares are delivered as described to GigCapital5’s transfer agent as described herein, then, if the Merger is consummated, GigCapital5 will redeem these shares for a pro rata portion of funds deposited in the Trust Account. If you exercise your Redemption Rights, then you will be exchanging your Public Shares for cash and you will cease to have any rights as a GigCapital5 stockholder (other than the right to receive the redemption amount) upon consummation of the Merger.

A GigCapital5 stockholder holding both Public Shares and Warrants may elect to redeem its Public Shares but not its Warrants. However, with respect to such holder’s Warrants, it may either sell such Warrants at any time in the open markets, or choose to retain such Warrants, which, if the proposed Business Combination closes, will become warrants of the Combined Company. If redemption occurs at an assumed $[●] per share in which all Public Shares are redeemed, such redeeming public stockholders will retain an aggregate of 23,000,000 detachable redeemable Warrants, which have an aggregate value of approximately $[●] based on the closing price of our detachable redeemable Warrants on the OTC Markets Group Inc. (the “OTC”) of $[●] on [●], 2023. See “The Public Stockholders will experience immediate dilution as a consequence of the issuance of the Combined Company Common Stock as consideration in the Proposed Business Combination, and will experience additional dilution following the Closing as a result of the issuance of Combined Company Common Stock (i) under the Equity Incentive Plan, (ii) pursuant to the exercise of the Assumed Warrants or (iii) pursuant to the future exercise of Warrants or Private Placement Warrants. Having a minority share position may reduce the influence that our current stockholders have on the management of the Combined Company.” and “Warrants, Private Placement Warrants and Assumed Warrants will become exercisable for Combined Company Common Stock, which would increase the number of shares eligible for future resale in the public market and result in dilution to our stockholders” for a discussion of the risks presented with respect to the Warrants.

18

All holders considering exercising Redemption Rights are urged to consult their tax advisor on the tax consequences to them of an exercise of Redemption Rights, including the applicability and effect of U.S. federal, state, local and non-U.S. tax laws. This proxy statement/prospectus shall not serve as an information statement for the stockholders of QT Imaging for purposes of understanding the tax consequences of the proposed Business Combination for such stockholders. If such an information statement is to be sent to QT Imaging stockholders, QT Imaging will separately prepare such document.

Following the Closing, GigCapital5 may redeem your Warrants prior to their exercise at a time that is disadvantageous to you. GigCapital5 will have the ability to redeem outstanding Warrants at any time after they become exercisable and prior to their expiration, at a price of $11.50 per Warrant, provided that the closing price of GigCapital5 Common Stock equals or exceeds $18.00 per share (as adjusted for adjustments to the number of shares issuable upon exercise or the exercise price of a warrant) for any 20 trading days within a 30 trading day period ending on the third trading day prior to proper notice of such redemption, provided that certain other conditions are met. If and when the Warrants become redeemable by us, we may exercise the redemption right even if we are unable to register or qualify the underlying securities for sale under all applicable state securities laws. As a result, GigCapital5 may redeem the Warrants as set forth above even if the holders are otherwise unable to exercise the warrants. Redemption of the outstanding Warrants could force you (i) to exercise your Warrants and pay the exercise price therefor at a time when it may be disadvantageous for you to do so, (ii) to sell your Warrants at the then-current market price when you might otherwise wish to hold your Warrants or (iii) to accept the nominal redemption price which, at the time the outstanding Warrants are called for redemption, is likely to be substantially less than the market value of your Warrants. None of the Private Placement Warrants will be redeemable by GigCapital5 so long as they are held by the Sponsor or its permitted transferees.

Historical trading prices for GigCapital5 Common Stock have varied between a low of approximately $9.80 per share on November 4, 2021 to a high of approximately $[●] per share on [●], 2023 but have not approached the $18.00 per share threshold for redemption (which, as described above, would be required for 20 trading days within a 30 trading-day period after they become exercisable and prior to their expiration, at which point the Warrants would become redeemable). In the event that GigCapital5 elects to redeem all of the redeemable Warrants as described above, GigCapital5 will fix a date for the redemption. Notice of redemption will be mailed by first class mail, postage prepaid, by us not less than 30 days prior to the redemption date to the registered holders of the Warrants to be redeemed at their last addresses as they appear on the registration books. Any notice mailed in the manner provided in the Warrant Agreement dated September 23, 2021, between GigCapital5 and Continental Stock Transfer & Trust Company, as warrant agent (the “Warrant Agreement”) shall be conclusively presumed to have been duly given whether or not the registered holder received such notice. In addition, beneficial owners of the redeemable warrants will be notified of such redemption by our posting of the redemption notice to The Depository Trust Company.

19

20

The Board Classification Charter Proposal: The affirmative vote (in person or by proxy) of the holders of a majority of the shares of GigCapital5 Common Stock entitled to vote thereon, voting as a single class, is required to approve the Board Classification Charter Proposal. Accordingly, a stockholder’s failure to vote by proxy or to vote in person (which would include presence at a virtual meeting) at the Stockholders’ Meeting, as well as an abstention from voting and a broker non-vote with regard to the Board Classification Charter Proposal, will have the same effect as a vote “AGAINST” such proposal. The Closing is conditioned on the approval of the Board Classification Charter Proposal, subject to the terms of the Business Combination Agreement. If the Business Combination Proposal is not approved, the Board Classification Charter Proposal will not be presented to the stockholders for a vote.

The Additional Charter Amendments in Connection with the Business Combination Proposal: The affirmative vote (in person or by proxy) of the holders of a majority of the shares of GigCapital5 Common Stock entitled to vote thereon, voting as a single class, is required to approve the Additional Charter Amendments in Connection with the Business Combination Proposal. Accordingly, a stockholder’s failure to vote by proxy or to vote in person (which would include presence at a virtual meeting) at the Stockholders’ Meeting, as well as an abstention from voting and a broker non-vote with regard to the Additional Charter Amendments in Connection with the Business Combination Proposal, will have the same effect as a vote “AGAINST” such proposal. The Closing is conditioned on the approval of the Additional Charter Amendments in Connection with the Business Combination Proposal, subject to the terms of the Business Combination Agreement. If the Business Combination Proposal is not approved, the Additional Charter Amendments in Connection with the Business Combination Proposal will not be presented to the stockholders for a vote.

The Director Election Proposal: The affirmative vote (in person or by proxy) of the holders of a plurality of the outstanding shares of GigCapital5 Common Stock entitled to vote thereon and actually cast at the Stockholders’ Meeting, is required to approve the Director Election Proposal. Accordingly, a stockholder’s failure to vote by proxy or to vote in person (which would include presence at a virtual meeting) at the Stockholders’ Meeting, as well as an abstention from voting and a broker non-vote with regard to the Director Election Proposal, will have no effect on the election of directors. If the Business Combination Proposal is not approved, the Director Election Proposal will not be presented to the stockholders for a vote.

The Nasdaq Proposal: The affirmative vote (in person or by proxy) of the holders of a majority of the shares of GigCapital5 Common Stock entitled to vote thereon and actually cast at the Stockholders’ Meeting, voting as a single class, is required to approve the Nasdaq Proposal. Accordingly, a stockholder’s failure to vote by proxy or to vote in person (which would include presence at a virtual meeting) at the Stockholders’ Meeting, as well as an abstention from voting and a broker non-vote with regard to the Nasdaq Proposal, will have no effect on the Nasdaq Proposal. The Closing is conditioned on the approval of the Nasdaq Proposal,

21

subject to the terms of the Business Combination Agreement. If the Business Combination Proposal is not approved, the Nasdaq Proposal will not be presented to the stockholders for a vote.

The Equity Incentive Plan Proposal: The affirmative vote (in person or by proxy) of the holders of a majority of the shares of GigCapital5 Common Stock entitled to vote thereon and actually cast at the Stockholders’ Meeting, voting as a single class, is required to approve the Equity Incentive Plan Proposal. Accordingly, a stockholder’s failure to vote by proxy or to vote in person (which would include presence at a virtual meeting) at the Stockholders’ Meeting, as well as an abstention from voting and a broker non-vote with regard to the Equity Incentive Plan Proposal, will have no effect on the Equity Incentive Plan Proposal. The Closing is conditioned on the approval of the Equity Incentive Plan Proposal, subject to the terms of the Business Combination Agreement. If the Business Combination Proposal is not approved, the Equity Incentive Plan Proposal will not be presented to the stockholders for a vote.

The Adjournment Proposal: The affirmative vote (in person or by proxy) of the holders of a majority of the shares of GigCapital5 Common Stock entitled to vote thereon and actually cast at the Stockholders’ Meeting, voting as a single class, is required to approve the Adjournment Proposal. Accordingly, a stockholder’s failure to vote by proxy or to vote in person (which would include presence at a virtual meeting) at the Stockholders’ Meeting, as well as an abstention from voting and a broker non-vote with regard to the Adjournment Proposal, will have no effect on the Adjournment Proposal. The Closing is not conditioned on the approval of the Adjournment Proposal.

As of [●], 2023, the Record Date, the Sponsor was entitled to vote the GigCapital5 Voting Shares. Such shares currently constitute approximately 68.3% of the outstanding shares of GigCapital5 Common Stock. The Sponsor has agreed to vote all of its shares of GigCapital5 Common Stock, in favor of each of the Proposals presented at the Stockholders’ Meeting, which is a sufficient amount to approve all of the Proposals. See “Other Agreements-Sponsor Support Agreement.”

These interests include, among other things:

22

23

24

There will be no finder’s fees, reimbursements or cash payments made by GigCapital5 to the Sponsor or GigCapital5’s officers or directors, or any of GigCapital5’s or its officers’ or directors’ affiliates, for services rendered to GigCapital5 prior to or in connection with the completion of the Business Combination, other than payment of the amount described above for office space, utilities, administrative and support services, and repayments of the Additional September 2022 Contributions and Additional March 2023 Contributions and any working capital loans made as a non-interest bearing note (the “Working Capital Note”) by our Sponsor or affiliates of our Sponsor to fund working capital deficiencies or finance transaction costs in connection with an initial business combination, which Working Capital Note will be repayable by GigCapital5 upon Closing. GigCapital5 currently has $[●] in a Working Capital Note. The Sponsor, in its discretion, may in lieu of having the Working Capital Note repaid upon the Closing, instead convert the Working Capital Note into units of GigCapital5, at a price of $10.00 per unit, upon the Closing, provided that the maximum amount that may be converted is no more than $1,500,000. The Sponsor and GigCapital5’s officers and directors or any of their respective affiliates will also be reimbursed for any out-of-pocket expenses incurred in connection with GigCapital5’s formation, the GigCapital5 IPO and activities on GigCapital5’s behalf such as identifying potential target businesses and performing due diligence on suitable business combinations. There is no cap or ceiling on the reimbursement of out-of-pocket expenses incurred by such persons in connection with activities on our behalf. As of the date of this prospectus, the Sponsor had not incurred any out-of-pocket expenses in connection with the proposed Business Combination that, as of such date, had not been reimbursed by GigCapital5 from GigCapital5’s working capital funds following the GigCapital5 IPO.

As of the date of this proxy statement/prospectus, the aggregate dollar value of the GigCapital5 securities held (based upon a value of $[●] per share of GigCapital5 Common Stock and $[●] per Warrant), loans extended, fees due, and out-of-pocket expenses for which the Sponsor and its affiliates have at risk that depend on completion of GigCapital5’s initial business combination is approximately $[●].

The GigCapital5 Board was aware of and considered these interests to the extent such interests existed at the time, among other matters, in approving the Business Combination Agreement and in recommending that the proposed Business Combination be approved by the stockholders of GigCapital5.

25

Under the rules of NYSE, brokers who hold shares in “street name” for a beneficial owner of those shares typically have the authority to vote in their discretion on “routine” proposals when they have not received instructions from beneficial owners. However, brokers are not permitted to exercise their voting discretion with respect to the approval of matters that the NYSE determines to be “non-routine” without specific instructions from the beneficial owner. It is expected that all proposals to be voted on at the Stockholders’ Meeting are “non-routine” matters. Broker non-votes occur when a broker or nominee is not instructed by the beneficial owner of shares to vote on a particular proposal for which the broker does not have discretionary voting power. If you are a GigCapital5 stockholder holding your shares in “street name” and you do not instruct your broker, bank or other nominee on how to vote your shares, your broker, bank or other nominee will not vote your shares on the Business Combination Proposal, the Board Classification Charter Proposal, the Additional Charter Amendments in Connection with the Business Combination Proposal, the Director Election Proposal, the Nasdaq Proposal, the Equity Incentive Plan Proposal, or the Adjournment Proposal. Such broker non-votes will be the equivalent of a vote “AGAINST” the Board Classification Charter Proposal and the Additional Charter Amendments in Connection with the Business Combination Proposal, but will have no effect on the vote count for such other Proposals.

If you are a GigCapital5 stockholder that attends the Stockholders’ Meeting virtually and fails to vote on the Board Classification Charter Proposal or the Additional Charter Amendments in Connection with the Business Combination Proposal, your failure to vote will have the same effect as a vote “AGAINST” such proposal.

If you are a GigCapital5 stockholder that attends the Stockholders’ Meeting virtually and fails to vote on the Business Combination Proposal, the Nasdaq Proposal, the Equity Incentive Plan Proposal, or the Adjournment Proposal, your failure to vote will have no effect on such Proposal.

26

If you are a stockholder of record of GigCapital5 and you choose to send a written notice or to mail a new proxy, you must submit your notice of revocation or your new proxy to GigCapital5, 1731 Embarcadero Rd., Suite 200, Palo Alto, CA 94303 and it must be received at any time before the vote is taken at the Stockholders’ Meeting. Any proxy that you submitted may also be revoked by submitting a new proxy by mail, or online or by telephone, not later than 11:59 p.m. prevailing Eastern Time on [●], 2023, or by voting at the Stockholders’ Meeting. Simply attending the Stockholders’ Meeting will not revoke your proxy. If your shares are held in “street name” or are in a margin or similar account, you should contact your broker for information on how to change or revoke your voting instructions, and must follow the directions you receive from your broker, bank or other nominee in order to change or revoke your vote.

c/o GigCapital5, Inc.

1731 Embarcadero Rd., Suite 200

Palo Alto, CA 94303

Attention: Secretary

Telephone: (650) 276-7040

27

You may also contact our proxy solicitor at:

Morrow Sodali LLC

333 Ludlow Street, 5th Floor, South Tower

Stamford, CT 06902

Telephone: (203) 658-9400 (Call Collect)

or

Call Toll-Free: (800) 662-5200

Email: GIA.info@investor.morrowsodali.com

To obtain timely delivery, our stockholders must request the materials no later than five business days prior to the Stockholders’ Meeting.

You may also obtain additional information about GigCapital5 from documents filed with the SEC by following the instructions in the section entitled “Where You Can Find More Information.”

If you are a holder of Public Shares and you intend to seek redemption of your Public Shares, you will need to deliver your shares of GigCapital5 Common Stock (either physically or electronically) to GigCapital5’s transfer agent at the address below prior to the vote at the Stockholders’ Meeting. If you have questions regarding the certification of your position or delivery of your stock, please contact:

Continental Stock Transfer & Trust Company

1 State Street, 30th Floor

New York, New York 10004

Attention: Mark Zimkind

E-mail: mzimkind@continentalstock.com

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58