Filed Pursuant to Rule 424(b)(3)
Registration No. 333-269268

PROSPECTUS SUPPLEMENT NO. 13

(to the Prospectus dated March 24, 2023)

MariaDB plc

16,351,314 Ordinary Shares Underlying Warrants

56,414,951 Ordinary Shares by selling holders

7,310,297 Warrants to Purchase Ordinary Shares by selling holders

This prospectus supplement updates, amends and supplements the prospectus, dated March 24, 2023 (the “Prospectus”), which forms a part of our registration statement on Form S-1 (No. 333-269268), with the information contained in our Current Report on Form 8-K filed with the Securities and Exchange Commission on October 10, 2023 (“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 an aggregate of up to 16,351,314 Ordinary Shares (as defined in the Prospectus), consisting of:

The Public Warrants, which are exercisable at a price of $11.50 per share, were originally sold as part of the APHC Public Units (as defined in the Prospectus) purchased by public investors in the APHC IPO (as defined in the Prospectus) at a price of $10.00 per APHC Public Unit. The Private Placement Warrants, which are exercisable at a price of $11.50 per share, were originally purchased by the Sponsor (as defined in the Prospectus) concurrent with the consummation of the APHC IPO at a price of $1.00 per warrant. Prior to the consummation of the Irish Domestication Merger (as defined in the Prospectus), 1,600,000 Private Placement Warrants were transferred by the Sponsor to the Syndicated Investors (as defined in the Prospectus) pursuant to the At Risk Capital Syndication (as defined in the Prospectus) (at a price per warrant of $1.00), and 5,710,297 Private Placement Warrants were transferred to the Sponsor’s co-founders, Lionyet International Ltd. (an entity owned and controlled by Shihuang “Simon” Xie) and Theodore T. Wang. The Kreos Warrants, which are exercisable at a price of €2.29 per share, were originally issued to Kreos (as defined in the Prospectus) by Legacy MariaDB (as defined in the Prospectus) in connection with a loan facility that is no longer outstanding. The Private Placement Warrants, the Public Warrants and the Kreos Warrants are sometimes referred to collectively in the Prospectus as the “Warrants.” To the extent that the Warrants are exercised for cash, we will receive the proceeds from such exercises.

The Prospectus and this prospectus supplement also relate to the offer and sale from time to time by the selling holders named in the Prospectus or their permitted transferees (the “selling holders”) of (i) up to 7,310,297 Private Placement Warrants and (ii) up to 56,414,951 Ordinary Shares, consisting of:

We are registering the Ordinary Shares and Private Placement Warrants that may be offered and sold by selling holders from time to time pursuant to their registration rights under certain agreements between us and the selling holders or their affiliates, as applicable.

This prospectus supplement is not complete without the Prospectus. This prospectus supplement should be read in conjunction with the Prospectus, including any amendments or supplements thereto, which is to be delivered with this prospectus supplement., 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 or supersedes the information contained therein. Capitalized terms used in this prospectus supplement and not otherwise defined herein have the meanings specified in the Prospectus.

Our Ordinary Shares and Public Warrants are listed on The New York Stock Exchange (“NYSE”) under the symbols “MRDB” and “MRDBW”, respectively. On October 9, 2023, the closing sale prices of our Ordinary Shares and Public Warrants were $0.6159 and $0.1425, respectively.

We are an “emerging growth company” and a “smaller reporting company” as defined under the U.S. federal securities laws and, as such, may elect to comply with certain reduced public company reporting requirements for this and future filings.

Investing in our Ordinary Shares and Warrants involves a high degree of risk. See the section entitled “Risk Factors” beginning on page 9 of the Prospectus.

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

The date of this prospectus supplement is October 10, 2023.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(D)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): October 10, 2023

MariaDB plc

(Exact name of registrant as specified in its charter)

699 Veterans Blvd

Redwood City, CA 94063

(Address of principal executive offices, including zip code)

(855) 562-7423

(Registrant’s telephone number, including area code)

Not Applicable

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

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

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

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

Emerging growth company x

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. ¨

The information set forth in Item 2.03 is incorporated by reference into this Item 1.01.

On October 10, 2023 (the “Closing Date”), MariaDB plc (the “Company”) issued a senior secured promissory note to RP Ventures LLC (“RP Ventures”), a Delaware limited liability company, in the principal amount of $26.5 million (the “Note”). RP Ventures will also act as the initial Agent as defined in the Note (in such capacity, the “Agent”).

The Note will mature on the earlier of (i) January 10, 2024, (ii) the occurrence of a Change of Control (as defined in the Note), (iii) the occurrence of any breach of any of the documentation relating to the Company’s loan from the European Investment Bank (the “EIB Loan”) or any demand for repayment of the EIB Loan, and (iv) the date on which the Note is otherwise declared due and payable pursuant to its terms. The proceeds of the Note will be used by the Company to repay all amounts outstanding under the EIB Loan, certain Note-related expenses, including expenses of RP Ventures, and for working capital purposes as approved by the Company’s board of directors (the “Board”). The Company will pay RP Ventures a nonrefundable funding fee of $132,500, and has agreed to pay or reimburse RP Ventures and Runa Capital Fund II, L.P. (“Runa”) for its out-of-pocket expenses related to the Note transaction. Runa currently beneficially owns approximately 8% of the outstanding ordinary shares of the Company. Michael Fanfant, the sole member and manager of RP Ventures, is a General Partner of Runa Capital, an affiliate of Runa. See Item 5.02 below for additional information.

Interest on the Note accrues on the principal amount at the rate of ten percent (10%) per annum and will be paid on a quarterly basis commencing on January 1, 2024. The Company may prepay any amounts due under the Note without penalty or premium, subject to the prior written consent of RP Ventures, provided that any prepayment of principal under the Note be accompanied by interest accrued and unpaid through the date of such prepayment. RP Ventures may demand immediate repayment of certain amounts outstanding under the Note if the Company or any of its subsidiaries incurs additional indebtedness or disposes, sells, or otherwise transfers any of their property or assets outside of the ordinary course of business, or if the Company or any of its subsidiaries receives any proceeds from the occurrence of a casualty event.

Until January 10, 2024, the Note restricts the Company from pursuing or accepting any offer with respect to any recapitalization, reorganization, merger, business combination, purchase, sale, loan, notes issuance, issuance of other indebtedness or other financing or similar transaction, or to any acquisition by any person or group, which would result in any person or group becoming the beneficial owner of 2% or more of any class of equity interests or voting power or consolidated net income, revenue or assets, of the Company, in each case other than with RP Ventures or Runa.

The Note provides that within five (5) business days after the Closing Date, the Company will retain a Chief Restructuring Officer to provide financial and operational services that must be satisfactory to the Agent. In addition, pursuant to the Note, the Company has appointed two directors selected by the Agent to the Board (the “New Board Members”). The Chief Restructuring Officer will report directly to the New Board Members. Further, as required by the Note, on the Closing Date, Harold Berenson, Alexander Suh, Christine Russell, and Theodore Wang resigned from the Board, and the size of the Board was fixed at four (4) directors. See Item 5.02 below for related information.

The Note contains certain customary representations and warranties and covenants of the Company. In addition, the Company has agreed to, among other things, provide to RP Ventures certain financial information, maintain minimum aggregate liquidity in an amount to be agreed upon after the Closing Date by the Board and the Agent, and make disbursements and collect receivables based on budget amounts.

The Note limits the ability of the Company to, among other things, (i) incur indebtedness, (ii) create certain liens, (iii) declare or distribute dividends or make certain other restricted payments, (iv) be party to a merger, consolidation, division or other fundamental change, (v) transfer, sell or lease Company assets, (vi) make certain modifications to the Company’s organizational documents or indebtedness, (vii) engage in certain transactions with affiliates, (viii) change the Company’s business, accounting or reporting practices, name or jurisdiction or organization, (ix) establish new bank accounts, and (x) establish or acquire any subsidiary. In addition, without the Agent’s prior consent, the Company will be restricted in, among other things, taking part in transactions outside of the ordinary course of its existing business, making certain payments, or issuing equity interests.

The Note provides for customary events of default, including for, among other things, payment defaults, breach of representations and certain covenants, cross defaults, insolvency, dissolution and bankruptcy, certain judgments against the Company, and material adverse changes. In the case of an event of default, RP Ventures may demand immediate repayment by the Company of all or part of the amounts outstanding, if any, under the Note.

In connection with issuance of the Note, the Company and MariaDB USA. Inc. and certain other of the Company’s subsidiaries (the “Guarantors”) entered into a Guarantee and Collateral Agreement (the “Security Agreement”), pursuant to which the Company and each Guarantor pledged substantially all of their respective assets as collateral for the Note and each Guarantor guaranteed to RP Ventures the payment of all obligations arising from the Note.

The foregoing description is only a summary of the material provisions of the Note and is qualified in its entirety by reference to the Note, a copy of which is filed as Exhibit 10.1 to this Current Report on Form 8-K (the “Current Report”) and incorporated by reference herein.

Under terms of the EIB Loan, transactions contemplated by the Note and the Security Agreement may allow the European Investment Bank to demand the Company immediately repay all amounts outstanding under the EIB Loan. Pursuant to the terms of the Note, and irrespective of any demand, the Company is obligated to use proceeds from the Note to repay the EIB Loan in full.

The information set forth in Item 2.03 is incorporated by reference into this Item 5.02.

On October 10, 2023, in connection with the closing of the transactions contemplated by the Note, each of Alexander Suh, Christine Russell, Harold Berenson, and Theodore Wang tendered their resignation from the Board and, to the extent applicable, all committees thereof, in each case, effective immediately. Current director Jurgen Ingels will serve as chair of the Board.

Also, on October 10, 2023, pursuant to the terms of the Note, Yakov “Jack” Zubarev and Michael Fanfant were appointed to the Board as Class II and I directors, respectively, with terms ending at the 2026 annual general meeting of shareholders and 2024 annual general meeting of shareholders, respectively. Additional biographical information, any applicable related party transactions, or other information will be provided in an amendment to this Current Report on Form 8-K.

The Company issued a press release on October 10, 2023, announcing transactions contemplated by the Note and the Board changes as described elsewhere in this Current Report. A copy of this press release is furnished as Exhibit 99.1 to this Current Report and incorporated herein by reference.

The information contained in Item 7.01 of this Current Report, including Exhibit 99.1 attached hereto, shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, nor shall it be deemed incorporated by reference into any registration statement or other filing pursuant to the Securities Act of 1933, as amended, except as otherwise expressly stated in the filing.

Forward-Looking Statements

Certain statements in this Current Report are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Words indicating future events and actions, such as “will,” “intend,” “plan,” and “may,” and variations of such words, and similar expressions and future-looking language identify forward-looking statements, but their absence does not mean that the statement is not forward-looking. The forward-looking statements in this periodic report include statements regarding the occurrence and timing of the disbursement of the advances under the Note, payment of the EIB Loan, and other use of proceeds, the retention of a chief restructuring officer and changes to Board composition, and related actions and events and the results therefrom, including those regarding the operations and trading of the Company. Forward-looking statements are not guarantees of future events and actions, which may vary materially from those expressed or implied in such statements. Differences may result from, among other things, actions taken by the Company or its management or the Board, or third parties, including those beyond the Company’s control. Such differences and uncertainties and related risks include, but are not limited to, the possibility that we may not timely receive the full amount under the Note as expected and any action taken in respect of a default under the EIB Loan and that the New York Stock Exchange may take action, including delisting, due to, among other things, the Company’s failure to meet Board, committee and other requirements of the exchange. The foregoing list of differences and risks and uncertainties is illustrative but by no means exhaustive. For more information on factors that may affect the Note and related events, please review “Risk Factors” and other information included in the Company’s filings and records filed with the United States Securities and Exchange Commission. These forward-looking statements reflect the Company’s expectations as of the date hereof. The Company undertakes no obligation to update the information provided herein.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.