Exhibit 10.6


UNIT SUBSCRIPTION AGREEMENT


 


This UNIT SUBSCRIPTION
AGREEMENT (this “Agreement”) is made as of the [•] day of [•] 2021, by and between Thunder Bridge
Capital Partners III Inc., a Delaware corporation (the “Company”), having its principal place of business at
9912 Georgetown Pike, Suite D203, Great Falls, Virginia 22066, and TBCP III, LLC, a Delaware limited liability company (the
“Subscriber”), having its principal place of business at 9912 Georgetown Pike, Suite D203, Great Falls, Virginia
22066.


 


WHEREAS, in connection
with the Company’s initial public offering of the Company’s units (the “IPO”), the Company desires
to sell to the Subscriber on a private placement basis (the “Offering”) an aggregate of 775,000 units (the “Initial
Units”) of the Company (or up to 865,000 Units if the over-allotment option in connection with the IPO is exercised in
full, comprised of the Initial Units and the Additional Units (as defined below)), each Unit comprised of one share of Class A
common stock of the Company, par value $0.0001 per share (“Common Stock”) and one quarter of one warrant, each
whole warrant exercisable to purchase one share of Common Stock (“Warrant”), for a purchase price of $10.00
per Unit. The shares of Common Stock underlying the Warrants are hereinafter referred to as the “Warrant Shares”.  The
shares of Common Stock underlying the Units (excluding the Warrant Shares) are hereinafter referred to as the “Placement
Shares.” The Warrants underlying the Units are hereinafter referred to as the “Placement Warrants.”  The
Units, Placement Shares, Placement Warrants and Warrant Shares, collectively, are hereinafter referred to as the “Securities.”  Each
whole Placement Warrant is exercisable to purchase one share of Common Stock at an exercise price of $11.50 during the period commencing
on the later of (i) twelve (12) months from the date of the closing of the Company’s IPO and (ii) 30 days following the consummation
of the Company’s initial business combination (the “Business Combination”), as such term is defined in
the registration statement in connection with the IPO, as amended at the time it becomes effective (the “Registration
Statement”), and expiring on the fifth anniversary of the consummation of the Business Combination or earlier upon redemption
or liquidation as described in the Registration Statement; and


 


WHEREAS, the Subscriber
wishes to purchase up to 865,000 Units, and the Company wishes to accept such subscription from Subscriber.


 


NOW, THEREFORE, in
consideration of the premises and the mutual covenants hereinafter set forth and other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, the Company and Subscriber hereby agree as follows:


 


	 	1.	Agreement to Subscribe


 


	 	1.1.	Purchase and Issuance of the Units.  Upon the terms and subject to the conditions of this Agreement, the Subscriber hereby agrees to purchase from the Company, and the Company hereby agrees to sell to the Subscriber, on the Initial Closing Date (as defined below) the Initial Units in consideration of the payment of the Purchase Price (as defined below). On the Initial Closing Date, the Company shall, at its option, deliver to the Subscriber the certificates representing the Securities purchased or effect such delivery in book-entry form.  


  


	 	1.2.(i)	Purchase Price. As payment in full for the Initial Units being purchased under this Agreement, the Subscriber shall pay $7,750,000 (the “Purchase Price”) by wire transfer of immediately available funds or by such other method as may be reasonably acceptable to the Company, to the trust account (the “Trust Account”) at a financial institution to be chosen by the Company, maintained by Continental Stock Transfer & Trust Company, acting as trustee (“Continental”), at least one (1) business day prior to the date of effectiveness of the Registration Statement.
	 	 	 
	 	1.2.(ii)	
        In the event that the over-allotment option
        is exercised in full or in part, Purchaser shall purchase up to an additional 90,000 Units (the “Additional Units”),
        in the same proportion as the amount of the over-allotment option that is exercised, and simultaneously with such purchase of Additional
        Units, as payment in full for the Additional Units being purchased hereunder, and at least one (1) business day prior to the
        closing of all or any portion of the over-allotment option, Purchaser shall pay $10.00 per Additional Unit, up to an aggregate
        amount of $900,000, by wire transfer of immediately available funds or by such other method as may be reasonably acceptable to
        the Company, to the Trust Account.

         



 






     


    


    

 


1.3.
Closing. The closing of the purchase and sale of the Units shall take place simultaneously with the closing of the IPO (the “Initial
Closing Date”). The closing of the purchase and sale of the Additional Units, if applicable, shall take place simultaneously
with the closing of all or any portion of the over-allotment option (such closing date, together with the Initial Closing Date,
the “Closing Dates” and each, a “Closing
Date”). The closing of the purchase and sale of each of the
Initial Units and the Additional Units shall take place at the offices of Ellenoff Grossman & Schole LLP, 1345 Avenue of the
Americas, 11th Floor, New York, New York, 10105, or such other place as may be agreed upon by the parties hereto.


 


1.4 Termination.
This Agreement and each of the obligations of the undersigned shall be null and void and without effect if the Initial Closing
Date does not occur prior to June 30, 2021.


 


		2.	Representations and Warranties of Subscriber



 


Subscriber represents and warrants to the
Company that:


 


2.1. No
Government Recommendation or Approval.  Subscriber understands that no federal or state agency has passed upon or
made any recommendation or endorsement of the Company or the Offering of the Securities.


 


2.2. Accredited
Investor. Subscriber represents that it is an “accredited investor” as such term is defined in Rule 501(a) of Regulation
D under the Securities Act of 1933, as amended (the “Securities Act”), and acknowledges that the sale contemplated
hereby is being made in reliance, among other things, on a private placement exemption to “accredited investors” under
the Securities Act and similar exemptions under state law.


 


2.3. Intent.  Subscriber
is purchasing the Securities solely for investment purposes, for Subscriber’s own account (and/or for the account or benefit
of its members or affiliates, as permitted, pursuant to the terms of an agreement (the “Insider Letter”) to
be entered into with respect to the Securities between, among others, Subscriber  and the Company, as described in the
Registration Statement), and not with a view to the distribution thereof and Subscriber has no present arrangement to sell the
Securities to or through any person or entity except as may be permitted under the Insider Letter.  Subscriber shall
not engage in hedging transactions with regard to the Securities unless in compliance with the Securities Act.


 


2.4. Restrictions
on Transfer.  Subscriber acknowledges and understands the Units are being offered in a transaction not involving a public
offering in the United States within the meaning of the Securities Act.  The Securities have not been registered under
the Securities Act and, if in the future Subscriber decides to offer, resell, pledge or otherwise transfer the Securities, such
Securities may be offered, resold, pledged or otherwise transferred only (A) pursuant to an effective registration statement
filed under the Securities Act, (B) pursuant to an exemption from registration under Rule 144 promulgated under the Securities
Act, if available, or (C) pursuant to any other available exemption from the registration requirements of the Securities Act,
and in each case in accordance with any applicable securities laws of any state or any other jurisdiction. Notwithstanding the
foregoing, Subscriber acknowledges and understands the Securities are subject to transfer restrictions as described in Section
8 hereof. Subscriber agrees that if any transfer of its Securities or any interest therein is proposed to be made, as a condition
precedent to any such transfer, Subscriber may be required to deliver to the Company an opinion of counsel satisfactory to the
Company with respect to such transfer. Absent registration or another available exemption from registration, Subscriber agrees
it will not resell the Securities (unless otherwise permitted pursuant to the Insider Letter, as described in the Registration
Statement).  Subscriber further acknowledges that because the Company is a shell company, Rule 144 may not be available
to Subscriber for the resale of the Securities until the one year anniversary following consummation of the initial Business Combination
of the Company, despite technical compliance with the requirements of Rule 144 and the release or waiver of any contractual transfer
restrictions.


 


2.5.
Sophisticated Investor.


 


(i) Subscriber
is sophisticated in financial matters and is able to evaluate the risks and benefits of the investment in the Securities.


 






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(ii) Subscriber is
aware that an investment in the Securities is highly speculative and subject to substantial risks because, among other things,
the Securities are subject to transfer restrictions and have not been registered under the Securities Act and therefore cannot
be sold unless subsequently registered under the Securities Act or an exemption from such registration is available. Subscriber
is able to bear the economic risk of its investment in the Securities for an indefinite period of time.


 


2.6. Independent
Investigation.  Subscriber, in making the decision to purchase the Units, has relied upon an independent investigation
of the Company and has not relied upon any information or representations made by any third parties or upon any oral or written
representations or assurances from the Company, its officers, directors or employees or any other representatives or agents of
the Company, other than as set forth in this Agreement. Subscriber is familiar with the business, operations and financial condition
of the Company and has had an opportunity to ask questions of, and receive answers from the Company’s officers and directors
concerning the Company and the terms and conditions of the offering of the Units and has had full access to such other information
concerning the Company as Subscriber has requested. Subscriber confirms that all documents that it has requested have been made
available and that Subscriber has been supplied with all of the additional information concerning this investment which Subscriber
has requested.


 


2.7 Organization
and Authority.  Subscriber is duly organized, validly existing and in good standing under the laws of the State of Delaware
and it possesses all requisite power and authority necessary to carry out the transactions contemplated by this Agreement.


 


2.8. Authority.
This Agreement has been validly authorized, executed and delivered by Subscriber and is a valid and binding agreement enforceable
in accordance with its terms, subject to the general principles of equity and to bankruptcy or other laws affecting the enforcement
of creditors’ rights generally.


 


2.9.
No Conflicts. The execution, delivery and performance of this Agreement and the consummation by Subscriber of the transactions
contemplated hereby do not violate, conflict with or constitute a default under (i) Subscriber’s charter documents,
(ii) any agreement or instrument to which Subscriber is a party or (iii) any law, statute, rule or regulation to which Subscriber
is subject, or any agreement, order, judgment or decree to which Subscriber is subject.


 


2.10. No Legal
Advice from Company.  Subscriber acknowledges it has had the opportunity to review this Agreement and the transactions
contemplated by this Agreement and the other agreements entered into between the parties hereto with Subscriber’s own legal
counsel and investment and tax advisors.  Except for any statements or representations of the Company made in this Agreement
and the other agreements entered into between the parties hereto, Subscriber is relying solely on such counsel and advisors and
not on any statements or representations of the Company or any of its representatives or agents for legal, tax or investment advice
with respect to this investment, the transactions contemplated by this Agreement or the securities laws of any jurisdiction.


 


2.11. Reliance
on Representations and Warranties.  Subscriber understands the Units are being offered and sold to Subscriber in reliance
on exemptions from the registration requirements under the Securities Act, and analogous provisions in the laws and regulations
of various states, and that the Company is relying upon the truth and accuracy of the representations, warranties, agreements,
acknowledgments and understandings of Subscriber set forth in this Agreement in order to determine the applicability of such provisions.


 


2.12. No General
Solicitation.  Subscriber is not subscribing for the Units as a result of or subsequent to any general solicitation or
general advertising, including but not limited to any advertisement, article, notice or other communication published in any newspaper,
magazine, or similar media or broadcast over television or radio, or presented at any seminar or meeting or in a registration statement
with respect to the IPO filed with the Securities and Exchange Commission (“SEC”).


 


2.13. Legend.  Subscriber
acknowledges and agrees the certificates evidencing each of the Securities shall bear a restrictive legend (the “Legend”),
in form and substance substantially as set forth in Section 4 hereof.


 






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		3.	Representations, Warranties and Covenants of the Company



 


The Company represents
and warrants to, and agrees with, Subscriber that:


 


3.1. Valid Issuance
of Capital Stock. The total number of shares of all classes of capital stock which the Company has authority to issue is 200,000,000
shares of Class A Common Stock, 20,000,000 shares of Class B Common Stock, $0.0001 par value per share (the “Class B Common
Stock”), and 1,000,000 shares of preferred stock, $0.0001 par value per share (“Preferred Stock”).
As of the date hereof, the Company has issued and outstanding 8,625,000 shares of Class B Common Stock (of which up to 1,125,000
shares are subject to forfeiture as described in the Registration Statement), no shares of Class A Common Stock and no shares of
Preferred Stock. All of the issued shares of capital stock of the Company have been duly authorized, validly issued, and are fully
paid and non-assessable.


 


3.2 Title
to Securities.  Upon issuance in accordance with, and payment pursuant to, the terms hereof and that certain warrant
agreement to be entered into between the Company and Continental, as warrant agent (the “Warrant Agreement”),
as the case may be, each of the Units, Placement Shares, Placement Warrants and Warrant Shares will be duly and validly issued,
fully paid and non-assessable. On the date of issuance of the Units and Warrant Shares shall have been reserved for issuance. Upon
issuance in accordance with, and payment pursuant to, the terms hereof and the Warrant Agreement, as the case may be, Subscriber
will have or receive good title to the Units, Placement Shares and Placement Warrants, free and clear of all liens, claims and
encumbrances of any kind, other than (i) transfer restrictions hereunder and pursuant to the Insider Letter and (ii) transfer restrictions
under federal and state securities laws.


 


3.3. Organization
and Qualification. The Company is a corporation duly incorporated, validly existing and in good standing under the laws of the
State of Delaware and has the requisite corporate power to own its properties and assets and to carry on its business as now being
conducted.


 


3.4. Authorization;
Enforcement. (i) The Company has the requisite corporate power and authority to enter into and perform its obligations under
this Agreement and to issue the Securities in accordance with the terms hereof, (ii) the execution, delivery and performance
of this Agreement by the Company and the consummation by it of the transactions contemplated hereby have been duly authorized by
all necessary corporate action, and no further consent or authorization of the Company or its Board of Directors or stockholders
is required, and (iii) this Agreement constitutes valid and binding obligations of the Company enforceable against the Company
in accordance with its terms, except as such enforceability may be limited by applicable bankruptcy, insolvency, fraudulent conveyance,
moratorium, reorganization, or similar laws relating to, or affecting generally the enforcement of, creditors’ rights and
remedies or by equitable principles of general application and except as enforcement of rights to indemnity and contribution may
be limited by federal and state securities laws or principles of public policy.


 


3.5. No Conflicts.
The execution, delivery and performance of this Agreement and the consummation by the Company of the transactions contemplated
hereby do not (i) result in a violation of the Company’s certificate of incorporation or by-laws, (ii) conflict
with, or constitute a default under any agreement or instrument to which the Company is a party or (iii) any law statute, rule
or regulation to which the Company is subject or any agreement, order, judgment or decree to which the Company is subject. Other
than any SEC or state securities filings which may be required to be made by the Company subsequent to the Closing, and any registration
statement which may be filed pursuant thereto, the Company is not required under federal, state or local law, rule or regulation
to obtain any consent, authorization or order of, or make any filing or registration with, any court or governmental agency or
self-regulatory entity in order for it to perform any of its obligations under this Agreement or issue the Units, Placement Shares,
Placement Warrants or Warrant Shares in accordance with the terms hereof.


 






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		4.	Legends



 


4.1 .Legend.
The Company will issue the Units, Placement Shares and Placement Warrants, and when issued, the Warrant Shares, purchased by the
Subscriber in the name of the Subscriber. The Securities will bear the following Legend and appropriate “stop transfer”
instructions:


 


“THE
SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”),
OR ANY STATE SECURITIES LAWS AND NEITHER THE SECURITIES NOR ANY INTEREST THEREIN MAY BE OFFERED, SOLD, TRANSFERRED, PLEDGED OR
OTHERWISE DISPOSED OF EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OR SUCH LAWS OR AN EXEMPTION
FROM REGISTRATION UNDER THE SECURITIES ACT AND SUCH LAWS WHICH, IN THE OPINION OF COUNSEL FOR THIS CORPORATION, IS AVAILABLE.”


 


“THE
SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO LOCKUP PURSUANT TO AN INSIDER LETTER BETWEEN, AMONG OTHERS, THUNDER BRDIGE
CAPITAL PARTNERS III INC. AND TBCP III, LLC AND MAY ONLY BE OFFERED, SOLD, TRANSFERRED, PLEDGED OR OTHERWISE DISPOSED DURING THE
TERM OF THE LOCKUP PURSUANT TO THE TERMS SET FORTH IN THE INSIDER LETTER.”


 


“THE
SECURITIES REPRESENTED HEREBY SHALL BE ENTITLED TO REGISTRATION RIGHTS UNDER A REGISTRATION RIGHTS AGREEMENT WITH THE CORPORATION.”


 


4.2. Subscriber’s
Compliance. Nothing in this Section 4 shall affect in any way Subscriber’s obligations and agreements to comply with
all applicable securities laws upon resale of the Securities.


 


4.3. Company’s
Refusal to Register Transfer of the Securities.  The Company shall refuse to register any transfer of the Securities,
if in the sole judgment of the Company such purported transfer would not be made (i) pursuant to an effective registration
statement filed under the Securities Act, or pursuant to an available exemption from the registration requirements of the Securities
Act and (ii) in compliance herewith and with the Insider Letter.


 


4.4 Registration
Rights.  The Subscriber will be entitled to certain registration rights which will be governed by a registration rights
agreement (“Registration Rights Agreement”) to be entered into between, among others, the Subscriber and the
Company, on or prior to the effective date of the Registration Statement. 


 


		5.	Waiver of Liquidation Distributions.



 


In connection with
the Securities purchased pursuant to this Agreement, Subscriber hereby waives any and all right, title, interest or claim of any
kind in or to any distributions of the amounts in the Trust Account with respect to the Securities, whether (i) in connection with
the exercise of redemption rights if the Company consummates the Business Combination, (ii) in connection with any tender offer
conducted by the Company prior to a Business Combination, (iii) upon the Company’s redemption of shares of Common Stock sold
in the Company’s IPO upon the Company’s failure to timely complete the Business Combination or (iv) in connection with
a stockholder vote to approve an amendment to the Company’s amended and restated certificate of incorporation (A) to modify
the substance or timing of the Company’s obligation to redeem 100% of the Company’s public shares if the Company does
not timely complete the Business Combination or (B) with respect to any other provision relating to stockholders’ rights
or pre-Business Combination activity.  In the event a Subscriber purchases shares of Common Stock in the IPO or in the
aftermarket, any additional shares so purchased shall be eligible to receive the redemption value of such shares of Common Stock
upon the same terms offered to all other purchasers of Common Stock in the IPO in the event the Company fails to consummate the
Business Combination.


  


		6.	Terms of Placement Warrants. Each Placement Warrant
shall have the terms set forth in the Warrant Agreement.



 


		7.	[Reserved].



  


		8.	Terms of the Units and Placement Warrants



 


8.1 The Units and their
component parts are substantially identical to the units to be offered in the IPO except that: (i) the Units and component parts
will be subject to transfer restrictions described in the Insider Letter, (ii) the Placement Warrants will be non-redeemable so
long as they are held by the initial holder thereof (or any of its permitted transferees), and may be exercisable on a “cashless”
basis if held by a Subscriber or its permitted transferees, as further described in the Warrant Agreement and (iii) the Units and
component parts are being purchased pursuant to an exemption from the registration requirements of the Securities Act and will
become freely tradable only after the expiration of the lockup described above in clause (i) and they are registered pursuant to
the Registration Rights Agreement to be signed on or before the date of the Prospectus or an exemption from registration is available.


 






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8.2 Subscriber agrees
to vote the Placement Shares in accordance with the terms of the Insider Letter and as otherwise described in the Registration
Statement.


 


		9.	Governing Law; Jurisdiction; Waiver of Jury
Trial



 


This Agreement shall
be governed by and construed in accordance with the laws of the State of New York for agreements made and to be wholly performed
within such state. The parties hereto hereby waive any right to a jury trial in connection with any litigation pursuant to this
Agreement and the transactions contemplated hereby.


  


		10.	Assignment; Entire Agreement; Amendment



 


10.1. Assignment.
Neither this Agreement nor any rights hereunder may be assigned by any party to any other person other than by a Subscriber to
a person agreeing to be bound by the terms hereof.


 


10.2. Entire
Agreement. This Agreement sets forth the entire agreement and understanding between the parties as to the subject matter thereof
and merges and supersedes all prior discussions, agreements and understandings of any and every nature among them.


 


10.3. Amendment.
Except as expressly provided in this Agreement, neither this Agreement nor any term hereof may be amended, waived, discharged or
terminated other than by a written instrument signed by all of the parties hereto.


 


10.4. Binding
upon Successors. This Agreement shall be binding upon and inure to the benefit of the parties hereto and to their respective heirs,
legal representatives, successors and permitted assigns. 


 


		11.	Notices



 


11.1 Notices.
Unless otherwise provided herein, any notice or other communication to a party hereunder shall be sufficiently given if in writing
and personally delivered or sent by facsimile or other electronic transmission with copy sent in another manner herein provided
or sent by courier (which for all purposes of this Agreement shall include Federal Express or other recognized overnight courier)
or mailed to said party by certified mail, return receipt requested, at its address provided for herein or such other address as
either may designate for itself in such notice to the other.  Communications shall be deemed to have been received when
delivered personally, on the scheduled arrival date when sent by next day or 2nd-day courier service, or if sent by facsimile upon
receipt of confirmation of transmittal or, if sent by mail, then three days after deposit in the mail. If given by electronic transmission,
such notice shall be deemed to be delivered (a) if by electronic mail, when directed to an electronic mail address at which
the stockholder has consented to receive notice; (b) if by a posting on an electronic network together with separate notice
to the stockholder of such specific posting, upon the later of (1) such posting and (2) the giving of such separate notice;
and (c) if by any other form of electronic transmission, when directed to the stockholder.


 


		12.	Counterparts



 


This Agreement may
be executed in one or more counterparts, all of which when taken together shall be considered one and the same agreement and shall
become effective when counterparts have been signed by each party and delivered to the other party, it being understood that both
parties need not sign the same counterpart. In the event that any signature is delivered by facsimile transmission or by e-mail
delivery of a “pdf” format data file, such signature shall create a valid and binding obligation of the party executing
(or on whose behalf such signature is executed) with the same force and effect as if such facsimile or “.pdf” signature
page were an original thereof.


 






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		13.	Survival; Severability



 


13.1. Survival.
The representations, warranties, covenants and agreements of the parties hereto shall survive the Closing Date.


 


13.2. Severability.
In the event that any provision of this Agreement becomes or is declared by a court of competent jurisdiction to be illegal, unenforceable
or void, this Agreement shall continue in full force and effect without said provision; provided that no such severability shall
be effective if it materially changes the economic benefit of this Agreement to any party.


 


		14.	Headings.



 


The titles and subtitles
used in this Agreement are used for convenience only and are not to be considered in construing or interpreting this Agreement.


 


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IN WITNESS WHEREOF,
the parties hereto have executed this Agreement to be effective as of the date first set forth above.


 


	 	COMPANY:
	 	 
	 	THUNDER BRIDGE CAPITAL PARTNERS III INC.
	 	 	 
	 	By:	 
	 	 	Name: Gary A. Simanson
	 	 	Title:   President and Chief Executive Officer


 


	 	SUBSCRIBER:
	 	 
	 	TBCP III, LLC
	 	 	 
	 	By:	 
	 	 	Name: Gary A. Simanson
	 	 	Title:   Managing Member


 


[Unit Subcription Agreement with Sponsor]