Form 424B5 - Prospectus [Rule 424(b)(5)]

PROSPECTUS SUPPLEMENT

(To Prospectus dated December 12, 2023)

Filed Pursuant to Rule 424(b)(5)

Registration No. 333-275840

Castellum, Inc.

5,243,967 Shares of Common Stock

Pre-Funded Warrants to Purchase up to 3,193,534 Shares of Common Stock

3,193,534 Shares of Common Stock Underlying the Pre-Funded Warrants

We are offering to a single institutional investor 5,243,967 shares of common stock, par value $0.0001 per share (“Common Stock”), in this offering. Each share of Common Stock is being sold at a price of $0.32.

We are also offering pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to an aggregate of 3,193,534 shares of Common Stock underlying the Pre-Funded Warrants to investors whose purchase of Common Stock in this offering would otherwise result in such purchaser, together with its affiliates and certain related parties, beneficially owning more than 9.99% of our Common Stock immediately following the closing of this offering. Subject to limited exceptions, the holder of Pre-Funded Warrants will not have the right to exercise any portion of its Pre-Funded Warrants if the holder, together with its affiliates, would beneficially own in excess of 9.99% of the number of Common Stock outstanding immediately after giving effect to such exercise. This offering also relates to the shares of Common Stock issuable upon exercise of the Pre-Funded Warrants sold in this offering. Each Pre-Funded Warrant is being sold at a price of $0.319. Each Pre-Funded Warrant will have an exercise price per share of Common Stock equal to $0.001 and is exercisable at any time after its original issuance until exercised in full.

In a concurrent private placement, we are also selling to the purchasers of our Common Stock and Pre-Funded Warrants in this offering, warrants to purchase an aggregate of 8,437,501 shares of Common Stock (the “Private Placement Warrants”). Each Private Placement Warrant will have an exercise price of $0.35 per share of Common Stock and is exercisable as of the date of Shareholder Approval (as defined therein) for a term of 5 years. The Private Placement Warrants and Common Stock issuable upon exercise of the Private Placement Warrants are not being registered under the Securities Act of 1933, as amended (the “Securities Act”), are not being offered pursuant to this prospectus supplement and the accompanying prospectus and are being offered pursuant to the exemption from registration provided in Section 4(a)(2) under the Securities Act and/or Rule 506(b) promulgated thereunder.

Our Common Stock is listed on the NYSE American LLC (the “NYSE American”) under the symbol “CTM”. On January 25, 2024, the last reported sale prices of our Common Stock on the NYSE American was $0.28. There is no established trading market for the Pre-Funded Warrants, and we do not expect a market to develop. We do not intend to apply for a listing for any such warrants on any securities exchange or other nationally recognized trading system. Without an active trading market, the liquidity of the Pre-Funded Warrants will be limited.

We have retained Maxim Group LLC, referred to herein as “Maxim” or the “placement agent”, to act as our exclusive placement agent in connection with the securities offered by this prospectus supplement and the accompanying prospectus. The placement agent has no obligation to buy any of the securities from us or to arrange for the purchase or sale of any specific number or dollar amount of securities. We have agreed to pay the placement agent the placement agent fees set forth in the table below, which assumes that we sell all of the securities we are offering. See “Plan of Distribution” beginning on page S-17 of this prospectus supplement for more information regarding these arrangements.

As of the date of this prospectus supplement, the aggregate market value of our outstanding shares of Common Stock held by non-affiliates was $6,309,097 based on 47,672,427 shares of Common Stock outstanding, of which 25,139,938 shares were held by non-affiliates, based on a price of $0.39 per share, which was the last reported sale price of our Common Stock on the NYSE American on January 19, 2024. As of the date of this prospectus supplement, we have not sold any securities pursuant to General Instruction I.B.6. of Form S-3 during the prior 12 calendar month period that ends on, and includes, the date of this prospectus supplement.

Investing in our securities involves a high degree of risk. Before making any decision to invest in our securities, you should carefully consider the information disclosed in this this prospectus supplement and the accompanying prospectus, including the information under “Risk Factors” beginning on page S-8 of this prospectus supplement, as well as the information, including the risk factors contained or incorporated by reference to this prospectus supplement and the accompanying prospectus as described under the heading “Where You Can Find More Information.”

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE ADEQUACY OR ACCURACY OF THIS PROSPECTUS SUPPLEMENT AND THE ACCOMPANYING PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

There is no arrangement for funds to be received in escrow, trust, or similar arrangement.


	Per share of Common Stock		Per Pre-Funded Warrant		Total
Offering Price	$	0.32	$	0.319	$	2,696,807
Placement Agent Fees (1)	$	0.0224	$	0.0223	$	188,776
Proceeds, before expenses, to us (2)	$	0.2976	$	0.2967	$	2,508,031

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(1)We have agreed: (i) to pay a cash fee to the placement agent equal to 7% of the aggregate gross proceeds raised in this offering; and (ii) to reimburse certain expenses of the placement agent in connection with this offering. See “Plan of Distribution” beginning on page S-17 of this prospectus supplement for additional information regarding compensation paid to the placement agent.

(2)The amount of the offering proceeds to us as presented in this table does not give effect to any exercise of the Private Placement Warrants.

We expect that delivery of the shares of Common Stock and Pre-Funded Warrants being offered pursuant to this prospectus supplement and the accompanying base prospectus will be made on or about January 29, 2024, subject to satisfaction of customary closing conditions.

Maxim Group LLC

The date of this prospectus supplement is January 25, 2024.

TABLE OF CONTENTS


			Page
PROSPECTUS SUPPLEMENT
ABOUT THIS PROSPECTUS SUPPLEMENT			S-1
CAUTIONARY NOTE CONCERNING FORWARD-LOOKING STATEMENTS			S-3
PROSPECTUS SUPPLEMENT SUMMARY			S-4
THE OFFERING			S-6
RISK FACTORS			S-8
USE OF PROCEEDS			S-10
DIVIDEND POLICY			S-11
DILUTION			S-12
CONCURRENT PRIVATE PLACEMENT OF WARRANTS			S-13
DESCRIPTION OF THE SECURITIES WE ARE OFFERING			S-15
PLAN OF DISTRIBUTION			S-17
LEGAL MATTERS			S-18
EXPERTS			S-18
WHERE YOU CAN FIND MORE INFORMATION			S-18
INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE			S-19


			Page
PROSPECTUS: DATED DECEMBER 12, 2023
ABOUT THIS PROSPECTUS			1
AVAILABLE INFORMATION			2
OUR COMPANY			3
RISK FACTORS			4
CAUTIONARY NOTE REGARDING FORWARD LOOKING STATEMENTS			3
USE OF PROCEEDS			6
DIVIDEND POLICY			7
DESCRIPTION OF CAPITAL STOCK			8
DESCRIPTION OF WARRANTS			13
DESCRIPTION OF UNITS			16
LEGAL OWNERSHIP OF SECURITIES			17
PLAN OF DISTRIBUTION			20
LEGAL MATTERS			22
EXPERTS			22
INFORMATION INCORPORATED BY REFERENCE			23

You should rely only on the information we have provided or incorporated by reference in this prospectus or in any prospectus supplement. We have not authorized anyone to provide you with information different from that contained or incorporated by reference in this prospectus or in any prospectus supplement. This prospectus and any prospectus supplement is an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. You should assume that the information contained in this prospectus and in any prospectus supplement is accurate only as of their respective dates and that any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus or any prospective supplement or any sale of securities. The registration statement, including the exhibits and the

documents incorporated herein by reference, can be read on the website of the Securities and Exchange Commission, or “SEC,” or on our corporate website at https://investors.castellumus.com/overview/default.aspx as set forth in this prospectus under the heading “Available Information.”

This prospectus supplement is not an offer to sell or a solicitation of an offer to buy securities in any jurisdiction in which such offer or solicitation is illegal.

ABOUT THIS PROSPECTUS SUPPLEMENT

All references to the terms the “Company,” “we,” “us” or “our” in this prospectus supplement refer to Castellum, Inc., a Nevada corporation, unless the context requires otherwise.

This prospectus supplement and the accompanying base prospectus are part of a registration statement that we filed with the Securities and Exchange Commission (the “SEC”) on Form S-3 (File No. 333-275840) utilizing a “shelf” registration process. Each time we conduct an offering to sell securities under the accompanying base prospectus we will provide a prospectus supplement that will contain specific information about the terms of that offering, including the price, the amount of securities being offered, and the plan of distribution. The shelf registration statement was initially filed with the SEC on December 1, 2023, and was declared effective on December 12, 2023. This prospectus supplement describes the specific details regarding this offering and may add, update or change information contained in the accompanying base prospectus. The accompanying base prospectus provides general information about us and our securities, some of which, such as the section entitled “Plan of Distribution,” may not apply to this offering. This prospectus supplement and the accompanying base prospectus are an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. We are not making offers to sell or solicitations to buy our securities in any jurisdiction in which an offer or solicitation is not authorized or in which the person making that offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make an offer or solicitation.

If information in this prospectus supplement is inconsistent with the accompanying base prospectus or the information incorporated by reference with an earlier date, you should rely on this prospectus supplement. This prospectus supplement, together with the accompanying base prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying base prospectus, include all material information relating to this offering. You should assume that the information appearing in this prospectus supplement, the accompanying base prospectus and the documents incorporated by reference in this prospectus supplement and the accompanying base prospectus is accurate only as of the respective dates of those documents. Our business, financial condition, results of operations and prospects may have changed since those dates. You should carefully read this prospectus supplement, the accompanying base prospectus and the information and documents incorporated by reference herein and therein before making an investment decision. See “Where You Can Find More Information” in this prospectus supplement and in the accompanying base prospectus.

We have not, and the placement agent has not, authorized anyone to provide you with information that is different from that contained in this prospectus supplement, the accompanying base prospectus or in any free writing prospectus we may authorize to be delivered or made available to you. When you make a decision about whether to invest in our securities, you should not rely upon any information other than the information contained in or incorporated by reference into this prospectus supplement, the accompanying base prospectus or in any free writing prospectus that we may authorize to be delivered or made available to you. Neither the delivery of this prospectus supplement and the accompanying base prospectus nor the sale of our securities means that the information contained in this prospectus supplement, the accompanying base prospectus or any free writing prospectus is correct after the date of the respective dates of such documents.

For investors outside the United States: We have not, and the placement agent has not, taken any action that would permit this offering or possession or distribution of this prospectus supplement or the accompanying base prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus supplement or the accompanying base prospectus must inform themselves about, and observe any restrictions relating to, the offering of the securities covered hereby and the distribution of this prospectus supplement and the accompanying base prospectus outside the United States.

This prospectus supplement and the accompanying base prospectus contain summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the full text of the actual documents, some of which have been filed or will be filed with the SEC and incorporated by reference herein. See “Where You Can Find More Information” in this prospectus supplement. We further note that the representations, warranties and covenants

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made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference into this prospectus supplement or the accompanying base prospectus were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

This prospectus supplement and the accompanying base prospectus contain and incorporate by reference certain market data and industry statistics and forecasts that are based on studies sponsored by us, independent industry publications and other publicly available information. Although we believe these sources are reliable, estimates as they relate to projections involve numerous assumptions, are subject to risks and uncertainties, and are subject to change based on various factors, including those discussed under “Risk Factors” in this prospectus supplement and the accompanying base prospectus and under similar headings in the documents incorporated by reference herein and therein. Accordingly, investors should not place undue reliance on this information.

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CAUTIONARY NOTE CONCERNING FORWARD-LOOKING STATEMENTS

This prospectus and the documents incorporated by reference herein contain or may contain forward looking statements that involve risks and uncertainties. All statements other than statements of historical fact contained in this prospectus, including statements regarding future events, our future financial performance, business strategy and plans and objectives of management for future operations, are forward-looking statements. We have attempted to identify forward-looking statements by terminology including “anticipates,” “believes,” “can,” “continue,” “could,” “estimates,” “expects,” “intends,” “may,” “plans,” “potential,” “predicts,” “should,” or “will,” or the negative of these terms or other comparable terminology. Although we do not make forward looking statements unless we believe we have a reasonable basis for doing so, we cannot guarantee their accuracy. These statements are only predictions and involve known and unknown risks, uncertainties and other factors, including the risks outlined under “Risk Factors” or elsewhere in this prospectus, which may cause our or our industry’s actual results, levels of activity, performance or achievements expressed or implied by these forward-looking statements.

Forward-looking statements should not be read as a guarantee of future performance or results, and will not necessarily be accurate indications of the times at, or by which, that performance or those results will be achieved. Forward-looking statements are based on information available at the time they are made and/or management’s good faith belief as of that time with respect to future events, and are subject to risks and uncertainties that could cause actual performance or results to differ materially from what is expressed in or suggested by the forward-looking statements.

Forward-looking statements speak only as of the date they are made. You should not put undue reliance on any forward-looking statements. Except as required by law, we assume no obligation to update forward-looking statements to reflect actual results, changes in assumptions, or changes in other factors affecting forward-looking information, except to the extent required by applicable securities laws. If we do update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements.

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PROSPECTUS SUPPLEMENT SUMMARY

The following summary highlights selected information contained elsewhere in or incorporated by reference into this prospectus supplement and the accompanying prospectus. The summary may not contain all of the information that you should consider before investing in our securities. You should read the entire prospectus supplement and accompany prospectus, the registration statement of which this prospectus is a part, and the information incorporated by reference into this prospectus supplement in their entirety, including the “Risk Factors” and our financial statements and the related notes incorporated by reference into this prospectus, before purchasing our securities in this offering. See the “Risk Factors” section of this prospectus supplement beginning on page S-8 for a discussion of the risks involved in investing in our securities. Except as otherwise indicated herein or as the context otherwise requires, references in this prospectus supplement to the “Company,” “we,” “us,” and “our” refer to Castellum, Inc.

Corporate Overview

Castellum, Inc. is focused on acquiring and growing technology companies in the areas of cybersecurity, IT, electronic warfare, information warfare, and information operations with businesses in the defense, federal, civilian, and commercial markets. Services include intelligence analysis, software development, software engineering, program management, strategic and mission planning, information assurance, cybersecurity and policy support, and data analytics. These services are applicable to customers in the United States government (“USG”), financial services, healthcare, and other users of large data applications. They can be delivered to on-premises enclaves or customers who rely upon cloud-based infrastructures. The Company has worked with multiple business brokers and contacts within their business network to identify potential acquisitions. Due to our success in completing seven acquisitions over the previous four years and given our executive officers’ and key managers’ networks of contacts in the IT, telecom, cybersecurity, and defense sectors, we believe that we are well positioned to continue to execute our business strategy given a pipeline of identified and acquisition targets. Because of our executive officers’ and key managers’ prior experience growing businesses organically, we believe that we are well positioned to grow our existing business via internal growth as well. The Company has developed a qualified business opportunity (the “Opportunity Pipeline”). Although there can be no assurance that the Opportunity Pipeline can be converted to revenues, the Company expects that the total value of the Opportunity Pipeline to be approximately $550 million. The Opportunity Pipeline represents the revenue opportunity for the Company from potential future contracts obtained through organic growth from qualified customers based on the expected base year contract value plus the value of all option periods.

Our primary customers are agencies and departments of the USG. Our expertise and technology support national security missions and government modernization for intelligence, defense, and federal civilian customers. The demand for our expertise and technology, in large measure, is created by the increasingly complex network, systems, and information environments in which governments and businesses operate, and by the need to stay current with emerging technology while increasing productivity, enhancing security, and ultimately, improving performance.

We provide expertise and technology to enterprise and mission customers in support of national security missions and government modernization/transformation. Due to the nature of the work being executed for the USG the budgets are expected to continue to grow in support of bipartisan national security imperatives. The majority of contracted work is operational in nature and is funded on an on-going basis.

As a government contractor, Castellum both cooperates (as a teaming partner) and competes with many different companies. Sometimes, Castellum both teams with (on one contract) and competes against (on a different contract) the same company. Among others, Castellum competes with (and sometimes also teams with) Northrup Grumman, CACI, Peraton, and Booz-Allen Hamilton.

Corporate Information

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Nevada corporation (“Bayberry” and, as context requires, the “Bayberry Acquisition”). On February 23, 2021, Bayberry was dissolved with the Nevada Secretary of State as it was non-operational after the merger with the Company. On November 21, 2019, we acquired Corvus Consulting, LLC, (“Corvus”), a Virginia limited liability company. On December 26, 2019, following our acquisition of Corvus, we changed our name from BioNovelus, Inc. to Castellum, Inc.

Our principal executive offices are located at 3 Bethesda Metro Center, Suite 700, Bethesda, Maryland 20814. Our telephone number is (301) 961-4895 and our website address is www.castellumus.com. Our website and the information contained on, or accessible through, our website will not be deemed to be incorporated by reference into this prospectus and does not constitute part of this prospectus.

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THE OFFERING


Common Stock offered by us:						5,243,967 shares.

Pre-Funded Warrants offered by us:						Pre-Funded Warrants to purchase up to 3,193,534 shares. This offering also relates to the shares of Common Stock issuable upon exercise of the Pre-Funded Warrants sold in this offering.

Common Stock outstanding before this offering:						47,672,427 shares(1).

Common Stock outstanding after this offering:						56,109,928 shares, assuming all of the Pre-Funded Warrants issued in this offering are exercised(1).

Use of proceeds:						We intend to use the net proceeds from this offering for working capital and general corporate purposes. Please see the section entitled “Use of Proceeds” on page S-10 of this prospectus supplement for a more detailed discussion.

Risk factors:						An investment in our securities involves a high degree of risk. Please see the section entitled “Risk Factors” beginning on page S-8 of this prospectus supplement as well as the other information included in or incorporated by reference into this prospectus supplement and the accompanying prospectus for a discussion of factors that you should consider carefully before making an investment decision.

Dividend policy:						We have never declared or paid any cash dividends on our Common Stock. We do not anticipate paying any cash dividends in the foreseeable future.

National Securities Exchange Listing:						Our Common Stock is currently listed on the NYSE American under the symbol “CTM”. There is no established public trading market for the Pre-Funded Warrants and we do not expect a market to develop. In addition, we do not intend to apply to list the Pre-Funded Warrants on any national securities exchange or other nationally recognized trading system. Without an active trading market, the liquidity of the Pre-Funded Warrants will be limited.

Concurrent private placement:						In a concurrent private placement, we are selling to the purchasers the Private Placement Warrants to purchase 100% of the number of our Common Stock and Pre-Funded Warrants purchased by such investors in this offering, equal to up to 8,437,501 shares of Common Stock. We will receive proceeds from the concurrent private placement transaction of the Private Placement Warrants solely to the extent such warrants are exercised for cash. The Private Placement Warrants are exercisable as of the date of Shareholder Approval (as defined therein) at an exercise price of $0.35 per share and will expire five years from such date. The Private Placement Warrants and Common Stock issuable upon the exercise of the Private Placement Warrants are not being offered pursuant to this prospectus supplement and the accompanying prospectus and are being offered pursuant to the exemption from registration provided in Section 4(a)(2) under the Securities Act and/or Regulation D promulgated thereunder. There is no established public trading market for the Private Placement Warrants, and we do not expect a market to develop. We do not intend to apply for listing of the Private Placement Warrants on any securities exchange or other nationally recognized trading system. Without an active trading market, the liquidity of the Private Placement Warrants will be limited. See “Concurrent Private Placement of Warrants.”

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(1)The number of shares of our Common Stock to be outstanding after the offering is based on 47,672,427 shares of Common Stock outstanding as of January 25, 2024 and excludes, as of that date, the following:

•12,344,681 shares of Common Stock issuable upon the conversion of the outstanding principal under the amended and restated note payable to the Buckhout Charitable Revocable Trust of approximately $3.2 Million;

•700,000 shares of Common Stock issuable upon the conversion of the outstanding principal amount under the note payable to Crom Cortana Fund LLC

•587,500 shares of Common Stock issuable upon conversion of Series A Preferred Stock;

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•481,250 shares of Common Stock issuable upon conversion of Series C Preferred Stock;

•1,115,235 shares of Common Stock reserved for issuance under the Castellum, Inc. 2021 Stock Incentive Plan;

•7,123,438 shares of Common Stock issuable upon the exercise of options outstanding, with a weighted average exercise price of $2.57 per share;

•7,444,698 shares of Common Stock issuable upon the exercise of warrants outstanding, with a weighted average exercise price of $1.68 per share;and

•the shares of Common Stock issuable upon the exercise of the Private Placement Warrants.

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RISK FACTORS

Before making an investment decision, you should carefully consider the risks described in this prospectus supplement, together with all of the other information incorporated by reference into this prospectus supplement and the accompanying prospectus, including the risks described in our most recent Annual Report on Form 10-K, as well as any amendments thereto reflected in subsequent filings with the SEC, including our audited consolidated financial statements and corresponding management’s discussion and analysis. The risks mentioned below are presented as of the date of this prospectus supplement and we expect that these will be updated from time to time in our periodic and current reports filed with or furnished to the SEC, as applicable, which are incorporated herein by reference. Please refer to these subsequent reports for additional information relating to the risks associated with investing in our securities.

Our business, financial condition or results of operations could be materially adversely affected by any of these risks. Additional risks not presently known to us or that we currently deem immaterial may also impair our business operations. The trading price of our Common Stock could decline due to any of these risks, and you may lose all or part of your investment. This prospectus supplement, the accompanying prospectus and the incorporated documents also contain forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from those anticipated in these forward-looking statements as a result of certain factors, including the risks mentioned below. Forward-looking statements included in this prospectus supplement are based on information available to us on the date hereof, and all forward-looking statements in documents incorporated by reference are based on information available to us as of the date of each such document. We are under no obligation to update or alter such forward-looking statements whether as a result of new information, future events or otherwise, other than as required by applicable securities legislation.

Risks Relating to This Offering

Sales of our Common Stock by stockholders may have an adverse effect on the then prevailing market price of our Common Stock.

Sales of a substantial number of our Common Stock in the public market following this offering could cause the market price of our Common Stock to decline and could impair our ability to raise capital through the sale of additional equity securities. We cannot predict the effect that future sales of our Common Stock or other equity or equity-related securities would have on the market price of our Common Stock.

Management will have broad discretion as to the use of the net proceeds from this offering, and we may not use the proceeds effectively.

We intend to use the net proceeds from the sale of securities by us in this offering for working capital and general corporate purposes. Our management will have broad discretion as to the application of the net proceeds from this offering and could use them for purposes other than those contemplated at the time of this offering, as described below in the section entitled “Use of Proceeds,” or in ways that do not necessarily improve our operating results or enhance the value of our Common Stock. Our stockholders may not agree with the manner in which our management chooses to allocate and spend the net proceeds. Our failure to use these funds effectively could have a material adverse effect on our business and could cause the price of our securities to decline.

Investors in this offering will suffer immediate and substantial dilution in the net tangible book value per Common Stock.

A purchaser of securities in this offering will experience immediate and substantial dilution. Please see the section entitled “Dilution” for a more detailed discussion of the dilution you will incur in this offering.

We may require additional funding through further issuances of our Common Stock or other securities, which may negatively affect the market price of our Common Stock.

To operate our business, we may need to raise additional capital through sales of our Common Stock, securities exercisable for or convertible into our Common Stock or debt securities pursuant to which interest and/or principal

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payments may be satisfied through the issuance of our Common Stock. Future sales of such securities or our Common Stock could adversely affect the prevailing market price of our Common Stock and our ability to raise capital in the future, and may cause you to incur additional dilution.

We do not intend to pay dividends on our Common Stock so any returns will depend on appreciation in the price of our Common Stock.

We have never declared or paid any cash dividends on our Common Stock. We currently anticipate that we will retain future earnings, if any, for the development, operation and expansion of our business and do not anticipate declaring or paying any cash dividends for the foreseeable future. Any return to stockholders will, therefore, be limited to the appreciation of their respective shares. There is no guarantee that our Common Stock will appreciate in value or maintain the price at which you purchased them.

There is no public market for the Pre-Funded Warrants being offered by us in this offering.

There is no established public trading market for the Pre-Funded Warrants, and we do not expect a market to develop. In addition, we do not intend to apply to list the Pre-Funded Warrants on any national securities exchange or other nationally recognized trading system. Without an active market, the liquidity of the Pre-Funded Warrants will be limited.

The Pre-Funded Warrants are speculative in nature.

The Pre-Funded Warrants offered hereby do not confer any rights of share of Common Stock ownership on their holders, such as voting rights or the right to receive dividends, but rather merely represent the right to acquire shares of common stock at a fixed price. Specifically, commencing on the date of issuance, holders of the Pre-Funded Warrants may acquire the shares of common stock issuable upon exercise of such warrants at an exercise price of $0.35 per share of Common Stock. Moreover, following this offering, the market value of the Pre-Funded Warrants is uncertain and there can be no assurance that the market value of the Pre-Funded Warrants will equal or exceed their public offering prices. There can be no assurance that the market price of the shares of Common Stock will ever equal or exceed the exercise price of the Pre-Funded Warrants, and consequently, whether it will ever be profitable for holders of the Pre-Funded Warrants to exercise the Pre-Funded Warrants.

Holders of the Pre-Funded Warrants offered hereby will have no rights as common stockholders with respect to the shares of our Common Stock underlying the Pre-Funded Warrants until such holders exercise their Pre-Funded Warrants and acquire our Common Stock, except as otherwise provided in the Pre-Funded Warrants.

Until holders of the Pre-Funded Warrants acquire shares of our Common Stock upon exercise thereof, such holders will have no rights with respect to the shares of our Common Stock underlying such warrants, except to the extent that holders of such Pre-Funded Warrants will have certain rights to participate in distributions or dividends paid on our Common Stock as set forth in the Pre-Funded Warrants. Upon exercise of the Pre-Funded Warrants, the holders will be entitled to exercise the rights of a common stockholder only as to matters for which the record date occurs after the exercise date.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering and the concurrent private placement will be approximately $2.2 million, after deducting the placement agent fees and commissions and estimated offering expenses payable by us and excluding the proceeds we may receive from the exercise of the Private Placement Warrants issued in the concurrent private placement. We currently expect to use the net proceeds from this offering for working capital and general corporate purposes.

This expected use of the net proceeds from this offering represents our intentions based upon our current plans and business conditions, and our management will retain broad discretion as to the ultimate allocation of the proceeds. We may temporarily invest funds that we do not immediately need for these purposes in investment securities or use them to make payments on our borrowings.

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DIVIDEND POLICY

We have not declared or paid cash dividends on our common stock since our inception. Under Nevada law, we are prohibited from paying dividends if the distribution would result in our company not being able to pay its debts as they become due in the normal course of business if our total assets would be less than the sum of our total liabilities plus the amount that would be needed to pay the dividends, or if we were to be dissolved at the time of distribution to satisfy the preferential rights upon dissolution of stockholders whose preferential rights are superior to those receiving the distribution. Even if our board of directors (“Board”) decides to pay dividends, the form, the frequency, and the amount will depend upon our future operations and earnings, capital requirements and surplus, general financial condition, contractual restrictions and other factors that the Board may deem relevant. While our Board will make any future decisions regarding dividends, as circumstances surrounding us change, it currently does not anticipate that we will pay any cash dividends in the foreseeable future.

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DILUTION

If you invest in our securities in this offering, your interest will be diluted immediately to the extent of the difference between the effective offering price per share and the as-adjusted net tangible book value per share of Common Stock after this offering.

The net tangible book value of our Common Stock as of September 30, 2023, was approximately ($6.5 million), or approximately ($0.14) per share of Common Stock. Net tangible book value per share represents the amount of our total tangible assets less total liabilities divided by the total number of our Common Stock outstanding as of September 30, 2023.

After giving effect to the sale of 5,243,967 shares of Common Stock in this offering at an offering price of $0.32 per share and accompanying Private Placement Warrant, and Pre-Funded Warrants to purchase 3,193,534 shares of Common Stock in this offering at a price of $0.319 per Pre-Funded Warrant and accompanying Private Placement Warrant, and after deducting placement agent fees and estimated offering expenses payable by us, assuming the exercise of all Pre-Funded Warrants at the exercise price of $0.001 per share of Common Stock, our as adjusted net tangible book value as of September 30, 2023, would have been approximately ($4.3 million), or approximately ($0.08) per share of Common Stock. This represents an immediate increase in as adjusted net tangible book value of approximately $0.06 per share of Common Stock to our existing security holders and an immediate dilution in as adjusted net tangible book value of approximately $0.40 per share of Common Stock to the purchaser of securities in this offering, as illustrated by the following table:


Offering price per share Common Stock and accompanying Private Placement Warrant			$	0.32
Net tangible book value per share of Common Stock as of September 30, 2023	$	(0.14)
Increase in as adjusted net tangible book value per share of Common Stock attributable to the offering	$	0.06
As adjusted net tangible book value per share of Common Stock as of September 30, 2023 after giving effect to this offering			$	(0.08)
Dilution per share Common Stock to new investors participating in this offering			$	0.40

To the extent that outstanding exercisable options or warrants are exercised, you may experience further dilution. In addition, we may need to raise additional capital and to the extent that we raise additional capital by issuing equity or convertible debt securities your ownership will be further diluted.

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CONCURRENT PRIVATE PLACEMENT OF WARRANTS

Concurrently with the closing of the sale of Common Stock and Pre-Funded Warrants in this offering, we also expect to issue and sell to the investors the Private Placement Warrants to purchase an aggregate of up to 8,437,501 shares of Common Stock at an initial exercise price equal to $0.35 per share.

The Private Placement Warrants and the Common Stock issuable upon the exercise of the Private Placement Warrants are not being registered under the Securities Act, are not being offered pursuant to this prospectus supplement and the accompanying prospectus and are being offered pursuant to the exemption provided in Section 4(a)(2) under the Securities Act and Rule 506(b) promulgated thereunder. Accordingly, the purchasers may only sell Common Stock issued upon exercise of the Private Placement Warrants pursuant to an effective registration statement under the Securities Act covering the resale of those shares, an exemption under Rule 144 under the Securities Act, or another applicable exemption under the Securities Act.

Exercisability. The Private Placement Warrants will become exercisable upon receipt of shareholder approval, and expire five years thereafter. The Private Placement Warrants are exercisable, at the option of each holder, in whole or in part by delivering to us a duly executed exercise notice and, at any time a registration statement registering the issuance of the Common Stock underlying the Private Placement Warrants under the Securities Act is effective and available for the issuance of such shares, or an exemption from registration under the Securities Act is available for the issuance of such shares, by payment in full in immediately available funds for the number of Common Stock purchased upon such exercise. If at the time of exercise there is no effective registration statement registering, or the prospectus contained therein is not available for the issuance of the Common Stock underlying the Private Placement Warrants, then the Private Placement Warrants may also be exercised, in whole or in part, at such time by means of a cashless exercise, in which case the holder would receive upon such exercise the net number of common shares determined according to the formula set forth in the Private Placement Warrant.

Exercise Limitation. A holder will not have the right to exercise any portion of the Private Placement Warrant if the holder (together with its affiliates) would beneficially own in excess of 4.99% (or 9.99% upon the request of the investor) of the number of Common Stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the Private Placement Warrants. However, any holder may increase or decrease such percentage, provided that any increase will not be effective until the 61st day after such election.

Exercise Price. The Private Placement Warrants will have an exercise price of $0.35 per share. The exercise price is subject to appropriate adjustment in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications, or similar events affecting our common shares and also upon any distributions of assets, including cash, stock or other property to our stockholders.

Transferability. Subject to applicable laws, the Private Placement Warrants may be offered for sale, sold, transferred, or assigned without our consent.

Exchange Listing. There is no established public trading market for the Private Placement Warrants being issued in the concurrent private placement, and we do not expect a market to develop. We do not intend to apply for listing of the Private Placement Warrants on any securities exchange or other nationally recognized trading system. Without an active trading market, the liquidity of the Private Placement Warrants will be limited.

Fundamental Transactions. In the event of any fundamental transaction, as described in the Private Placement Warrants and generally including any merger with or into another entity, sale of all or substantially all of our assets, tender offer or exchange offer, or reclassification of our Common Stock, then upon any subsequent exercise of a Private Placement Warrant, the holder will have the right to receive as alternative consideration, for each Common Share that would have been issuable upon such exercise immediately prior to the occurrence of such fundamental transaction, the number of Common Stock of the successor or acquiring corporation or of our company, if it is the surviving corporation, and any additional consideration receivable upon or as a result of such transaction by a holder of the number of Common Stock for which the Private Placement Warrant is exercisable immediately prior to such event.

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Rights as a Stockholder. Except as otherwise provided in the Private Placement Warrants or by virtue of such holder’s ownership of our common shares, the holder of a Private Placement Warrant does not have the rights or privileges of a holder of our common shares, including any voting rights, until the holder exercises the Private Placement Warrant.

Registration Rights. We have agreed to file a registration statement covering the resale of the shares issuable upon the exercise of the Private Placement Warrants (the “Private Placement Warrant Shares”) within 90 days of the date of the securities purchase agreement entered into between the purchasers and us. We must use commercially reasonable efforts to cause such registration statement to become effective within 180 days following the closing date of the offering and to keep such registration statement effective at all times until the purchasers no longer own any Private Placement Warrants or Private Placement Warrant Shares.

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DESCRIPTION OF THE SECURITIES WE ARE OFFERING

We are offering 5,243,967 shares of Common Stock at an offering price of $0.32 per share and Pre-Funded Warrants to purchase up to 3,193,534 shares of Common Stock at an offering price of $0.319 per Pre-Funded Warrant (exercisable for Common Stock at an exercise price of $0.001 per share of Common Stock).

Common Stock

The material terms and provisions of our Common Stock and each other class of our securities that qualifies or limits our Common Stock are described under the caption “Description of Capital Stock” starting on page 8 of the accompanying prospectus.

Pre-Funded Warrants

The following is a summary of the material terms and provisions of the Pre-Funded Warrants that are being offered hereby. This summary is subject to and qualified in its entirety by the form of Pre-Funded Warrant, which has been provided to the investors in this offering and which will be filed with the SEC as an exhibit to a Current Report on Form 8-K in connection with this offering and incorporated by reference into the registration statement of which this prospectus supplement forms a part. Prospective investors should carefully review the terms and provisions of the form of Pre-Funded Warrants for a complete description of the terms and conditions of the Pre-Funded Warrants.

Duration and Exercise Price

The Pre-Funded Warrants offered hereby will have an exercise price of $0.001 per share. The Pre-Funded Warrants will be immediately exercisable and may be exercised at any time after their original issuance until such Pre-Funded Warrants are exercised in full. The exercise price and number of shares of Common Stock issuable upon exercise are subject to appropriate adjustment in the event of share dividends, share splits, reorganizations, or similar events affecting our Common Stock. Pre-Funded Warrants will be issued in certificated form only.

Exercisability

The Pre-Funded Warrants will be exercisable, at the option of each holder, in whole or in part, by delivering to us a duly executed exercise notice accompanied by payment in full for the number of Common Stock purchased upon such exercise (except in the case of a cashless exercise as discussed below). A holder (together with its affiliates) may not exercise any portion of such holder’s warrants to the extent that the holder would own more than 9.99% of our outstanding Common Stock immediately after exercise, except that upon at least 61 days’ prior notice from the holder to us, the holder may increase the amount of ownership of outstanding Common Stock after exercising the holder’s Pre-Funded Warrants up to 9.99% of the number of shares of Common Stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the Pre-Funded Warrants.

Cashless Exercise

In lieu of making the cash payment otherwise contemplated to be made to us upon the exercise of a Pre-Funded Warrant in payment of the aggregate exercise price, the holder may elect instead to receive upon such exercise (either in whole or in part) the net number of Common Stock shall be determined according to the formula set forth in the Pre-Funded Warrants.

Fundamental Transactions

In the event of any fundamental transaction, as described in the Pre-Funded Warrants and generally including any merger with or into another entity, sale of all or substantially all of our assets, tender offer, or exchange offer, or reclassification of our Common Stock, then upon any subsequent exercise of a Pre-Funded Warrant, the holder will have the right to receive as alternative consideration, for each Common Share that would have been issuable upon such exercise immediately prior to the occurrence of such fundamental transaction, the number of Common Stock of the successor or acquiring corporation or of our company, if it is the surviving corporation, and any additional

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consideration receivable upon or as a result of such transaction by a holder of the number of Common Stock for which the Pre-Funded Warrant is exercisable immediately prior to such event.

Transferability

In accordance with its terms and subject to applicable laws, a Pre-Funded Warrant may be transferred at the option of the holder upon surrender of the Pre-Funded Warrant to us together with the appropriate instruments of transfer and payment of funds sufficient to pay any transfer taxes (if applicable).

Fractional Shares

No fractional Common Stock will be issued upon the exercise of the Pre-Funded Warrants. Rather, the number of shares of Common Stock to be issued will, at our election, either be rounded up to the next whole share or we will pay a cash adjustment in respect of such final fraction in an amount equal to such fraction multiplied by the exercise price.

Trading Market

There is no established trading market for the Pre-Funded Warrants, and we do not expect a market to develop. We do not intend to apply for a listing for the Pre-Funded Warrants on any securities exchange or other nationally recognized trading system. Without an active trading market, the liquidity of the Pre-Funded Warrants will be limited.

Rights as a Stockholder

Except as otherwise provided in the Pre-Funded Warrants or by virtue of the holders’ ownership of shares of our Common Stock, the holders of Pre-Funded Warrants do not have the rights or privileges of holders of our shares of common stock, including any voting rights, until such Pre-Funded Warrant holders exercise their warrants.

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PLAN OF DISTRIBUTION

Pursuant to a placement agency agreement dated January 25, 2024 (the “Placement Agency Agreement”), we have engaged the placement agent to act as our exclusive placement agent, on a reasonable best efforts basis, in connection with this offering. Under the terms of the Placement Agency Agreement, Maxim Group LLC (“Maxim”) is not purchasing the securities offered by us in this offering, and is not required to sell any specific number or dollar amount of securities, but will assist us in this offering on a reasonable best-efforts basis. The terms of this offering were subject to market conditions and negotiations between us, Maxim and prospective investors. Maxim will have no authority to bind us by virtue of the Placement Agency Agreement. Maxim may engage sub-agents or selected dealers to assist with this offering. We may not sell the entire amount of the share of our Common Stock or Pre-Funded Warrants offered pursuant to this prospectus supplement.

On January 25, 2024, we entered into a securities purchase agreement directly with the investor in connection with this offering for the sale of an aggregate of 5,243,967 shares of Common Stock at an offering price of $0.32 per share and Pre-Funded Warrants to purchase up to 3,193,534 shares of Common Stock at an offering price of $0.319 per Pre-Funded Warrant (exercisable for Common Stock at an exercise price of $0.001 per share of Common Stock) pursuant to this prospectus supplement and the accompanying prospectus.

We expect to deliver the shares of our Common Stock and Pre-Funded Warrants being offered pursuant to this prospectus supplement on or about January 29, 2024.

Fees and Expenses

We have agreed to pay to the placement agent a cash fee equal to 7% of the aggregate gross proceeds raised in this offering. The following table shows the total placement agent cash fees we will pay in connection with the sale of the securities in this offering.


Per Share and Accompanying Warrant	Total
Placement Agent Fees	$	0.022	$	188,776

We have also agreed to reimburse the placement agent for all travel and other out-of-pocket expenses incurred, including the reasonable fees, costs, and disbursements of its legal counsel in respect of the offering of $60,000. We estimate the total offering expenses that will be payable by us, excluding the placement agent’s fees and expenses, will be approximately $241,274.

Lock-Up Agreements

Our directors and officers have entered into lock-up agreements. Under these agreements, these individuals have agreed, subject to specified exceptions, not to sell or transfer any shares of common stock or securities convertible into, or exchangeable or exercisable for, our common stock during a period ending 60 days after the closing date of this offering, without first obtaining the written consent of the placement agent.

We have also agreed in the purchase agreement, subject to certain exceptions, to a restriction on the issuance of any variable priced securities for 1 year following the date of the Share Purchase Agreement. We have also agreed to a lock-up that, subject to certain exceptions, prevents us from entering into any agreement to issue or announce the issuance or proposed issuance of any shares of common stock or securities convertible into, exchangeable for, exercisable for, or repayable with common stock or file any registration statement or amendment or supplement thereto for a period of 60 days after the closing date of this offering.

Indemnification

We have agreed to indemnify the placement agent and specified other persons against certain liabilities relating to or arising out of the placement agent’s activities under the placement agency agreement and to contribute to payments that the placement agent may be required to make in respect of such liabilities.

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Regulation M

The placement agent may be deemed to be an underwriter within the meaning of Section 2(a)(11) of the Securities Act, and any commissions received by it and any profit realized on the resale of the securities sold by it while acting as principal might be deemed to be underwriting discounts or commissions under the Securities Act. As an underwriter, the placement agent would be required to comply with the requirements of the Securities Act and the Exchange Act, including, without limitation, Rule 415(a)(4) under the Securities Act and Rule 10b-5 and Regulation M under the Exchange Act. These rules and regulations may limit the timing of purchases and sales of shares of common stock and warrants by the placement agent acting as principal. Under these rules and regulations, the placement agent:

•may not engage in any stabilization activity in connection with our securities; and

•may not bid for or purchase any of our securities or attempt to induce any person to purchase any of our securities, other than as permitted under the Exchange Act, until it has completed its participation in the distribution.

From time to time, Maxim may provide in the future various advisory, investment and commercial banking and other services to us in the ordinary course of business, for which they have received and may continue to receive customary fees and commissions. However, except as disclosed in this prospectus supplement, we have no present arrangements with Maxim for any further services.

LEGAL MATTERS

Certain legal matters relating to the offering of the securities under this prospectus supplement will be passed upon for us by Lucosky Brookman LLP, Woodbridge, New Jersey. Pryor Cashman LLP, New York, New York is acting as counsel to the placement agent in connection with this offering.

EXPERTS

Our consolidated financial statements as of December 31, 2022 and 2021 and for each of the years in the two-year period ended December 31, 2022 incorporated in this Prospectus by reference from the Company’s Annual Report on From 10-K for the year ended December 31, 2022 have been audited by RSM US LLP, an independent registered public accounting firm, as stated in their reports thereon, incorporated herein by reference, and have been incorporated in this Prospectus and Registration Statement in reliance upon such report and upon the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and periodic reports, proxy statements, and other information with the SEC using the SEC’s Electronic Data Gathering, Analysis, and Retrieval (“EDGAR”) system. The SEC maintains a web site that contains reports, proxy and information statements, and other information about issuers, such as us, who file electronically with the SEC. The address of that website is http://www.sec.gov.

Our website address is www.castellumus.com. The information on our website, however, is not, and should not be deemed to be, a part of this prospectus.

This prospectus and any prospectus supplement are part of a registration statement that we filed with the SEC and do not contain all of the information in the registration statement. This prospectus omits some of the information contained in the registration statement, and we refer you to the full registration statement for further information about us and the securities being offered by the selling stockholders under this prospectus. The full registration statement may be obtained from the SEC or us, as provided below. Forms of the documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement. Statements in this prospectus or any prospectus supplement about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the actual documents for a more complete description of the relevant matters. You may inspect a copy of the registration statement through the SEC’s website, as provided above.

S-18

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

Incorporation by Reference

We are “incorporating by reference” in this prospectus certain documents we file with the SEC, which means that we can disclose important information to you by referring you to those documents. The information in the documents incorporated by reference is considered to be part of this prospectus. Statements contained in documents that we file with the SEC and that are incorporated by reference in this prospectus will automatically update and supersede information contained in this prospectus, including information in previously filed documents or reports that have been incorporated by reference in this prospectus, to the extent the new information differs from or is inconsistent with the old information. We have filed or may file the following documents with the SEC and they are incorporated herein by reference as of their respective dates of filing.

•Our Annual Report on Form 10-K for the year ended December 31, 2022, filed with the SEC on March 17, 2023;

•The portions of the definitive proxy statement on Schedule 14A filed on April 10, 2023 for the Company’s 2023 Annual Meeting of Stockholders held on May 25, 2023 that are incorporated by reference into the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022;

•Our Quarterly Report on Form 10-Q for the period ended March 31, 2023, filed with the SEC on May 15, 2023

•Our Quarterly Report on Form 10-Q for the period ended June 30, 2023, filed with the SEC on August 14, 2023;

•Our Quarterly Report on Form 10-Q for the period ended September 30, 2023, filed with the SEC on November 14, 2023;

•Our Current Reports on Form 8-K or Form 8-K/A filed (not furnished) with the SEC on January 18, 2023, January 19, 2023, January 24, 2023, February 16, 2023, March 1, 2023, March 20, 2023, March 28, 2023, April 6, 2023, April 26, 2023, May 12, 2023, May 25, 2023, May 26, 2023, June 5, 2023, June 14, 2023, June 27, 2023, June 30, 2023, July 31, 2023, August 29, 2023, October 20, 2023, October 31, 2023, and November 27, 2023; and

•The description of our common stock, par value $0.0001 per share (the “Common Stock”) contained in our Registration Statement on Form 8-A, filed with the SEC on October 6, 2022 and any amendment or report filed for the purpose of updating such description.

All documents that we filed with the SEC pursuant to Sections 13(a), 13(c), 14, and 15(d) of the Exchange Act subsequent to the date of this registration statement and prior to the filing of a post-effective amendment to this registration statement that indicates that all securities offered under this prospectus have been sold, or that deregisters all securities then remaining unsold, will be deemed to be incorporated in this registration statement by reference and to be a part hereof from the date of filing of such documents.

Any statement contained in a document incorporated or deemed to be incorporated by reference in this prospectus shall be deemed modified, superseded, or replaced for purposes of this prospectus to the extent that a statement contained in this prospectus, or in any subsequently filed document that also is deemed to be incorporated by reference in this prospectus, modifies, supersedes, or replaces such statement. Any statement so modified, superseded, or replaced shall not be deemed, except as so modified, superseded, or replaced, to constitute a part of this prospectus. None of the information that we disclose under Items 2.02 or 7.01 of any Current Report on Form 8-K or any corresponding information, either furnished under Item 9.01 or included as an exhibit therein, that we may from time to time furnish to the SEC will be incorporated by reference into, or otherwise included in, this prospectus, except as otherwise expressly set forth in the relevant document. Subject to the foregoing, all information appearing in this prospectus is qualified in its entirety by the information appearing in the documents incorporated by reference.

S-19

You may request a free copy of any of the documents incorporated by reference in this prospectus (other than exhibits, unless they are specifically incorporated by reference in the documents) by writing or telephoning us at the following address:

Castellum, Inc.

3 Bethesda Metro Center, Suite 700

Bethesda, MD 20814

Telephone: (301) 961-4895

Exhibits to the filings will not be sent, however, unless those exhibits have specifically been incorporated by reference in this prospectus and any accompanying prospectus supplement and the information on our website is not a part of this prospectus and is not incorporated by reference.

S-20

PROSPECTUS

CASTELLUM, INC.

$10,000,000 of

Common Stock

Preferred Stock

Warrants

Rights

Units

Offered by the Company

1,425,000 Shares of Common Stock

Offered by the Selling Stockholders

We may offer and sell up to $10 million in the aggregate of the securities identified above from time to time in one or more offerings. The selling stockholders may offer and sell up to 1,425,000 shares in the aggregate of the Company’s common stock, par value $0.0001 (the “Common Stock”). The 1,425,000 shares consists of: (a) 25,000 shares of Common Stock currently held by the selling stockholder; (b) 700,000 shares of Common Stock underlying a warrant issued by the Company to the selling stockholders in February 2023; and (c) 700,000 shares of Common Stock underlying a convertible promissory note issued by the Company to the selling stockholders in February 2023.This prospectus provides you with a general description of the securities. We will not receive any proceeds from the sale of our Common Stock by the selling stockholders.

Each time we or the selling stockholders offer(s) and sell(s) securities, we or such selling stockholders will provide a supplement to this prospectus that contains specific information about the offering and, if applicable, the selling stockholders, as well as the amounts, prices and terms of the securities. The supplement may also add, update or change information contained in this prospectus with respect to that offering. You should carefully read this prospectus and the applicable prospectus supplement before you invest in any of our securities.

We may offer and sell the securities described in this prospectus and any prospectus supplement to or through one or more underwriters, dealers and agents, or directly to purchasers, or through a combination of these methods. In addition, the selling stockholders may offer and sell shares of our Common Stock from time to time, together or separately. If any underwriters, dealers, or agents are involved in the sale of any of the securities, their names and any applicable purchase price, fee, commission, or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. See the sections of this prospectus entitled “About this Prospectus” and “Plan of Distribution” for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

INVESTING IN OUR SECURITIES INVOLVES RISKS. SEE THE “RISK FACTORS” ON PAGE 4 AND THE RISK FACTORS IN OUR MOST RECENT ANNUAL REPORT ON FORM 10-K, WHICH IS INCORPORATED BY REFERENCE HEREIN, AS WELL AS IN ANY OTHER RECENTLY FILED QUARTERLY OR CURRENT REPORTS AND, IF ANY, IN THE RELEVANT PROSPECTUS SUPPLEMENT. WE URGE YOU TO CAREFULLY READ THIS PROSPECTUS AND THE ACCOMPANYING PROSPECTUS SUPPLEMENT, TOGETHER WITH THE DOCUMENTS WE INCORPORATE BY REFERENCE, DESCRIBING THE TERMS OF THESE SECURITIES BEFORE INVESTING.

The aggregate market value of our outstanding common stock held by non-affiliates is $11,843,207 based on 47,672,427 shares of outstanding common stock, of which 25,113,938 are held by affiliates, and a per share price of $0.525 based on the closing sale price of our common stock on October 31, 2023. Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell our common stock in a public primary offering with a value exceeding more than one-third of our public float in any 12-month period so long as our public float remains below $75,000,000. We have not offered any securities pursuant to General Instruction I.B.6. of Form S-3 during the prior 12 calendar month period that ends on and includes the date of this prospectus.

Our common stock is listed on the NYSE American LLC (the “NYSE American”) under the symbol “CTM”. On November 30, 2023, the last reported sale price of our common stock on the NYSE American was $0.22 per share.

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

The date of this prospectus is December 12, 2023

TABLE OF CONTENTS


			Page
ABOUT THIS PROSPECTUS			1
AVAILABLE INFORMATION			2
OUR COMPANY			3
RISK FACTORS			4
CAUTIONARY NOTE REGARDING FORWARD LOOKING STATEMENTS			5
USE OF PROCEEDS			6
DIVIDEND POLICY			7
DESCRIPTION OF CAPITAL STOCK			8
DESCRIPTION OF WARRANTS			13
DESCRIPTION OF UNITS			16
LEGAL OWNERSHIP OF SECURITIES			17
PLAN OF DISTRIBUTION			20
LEGAL MATTERS			22
EXPERTS			22
INFORMATION INCORPORATED BY REFERENCE			23

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the U.S. Securities and Exchange Commission, or the SEC, using a “shelf” registration process. By using a shelf registration statement, we may sell securities from time to time and in one or more offerings up to a total dollar amount of $10,000,000, and the selling stockholders may, from time to time, sell up to 1,425,000 shares of Common Stock as described in this prospectus.

Each time that we or the selling stockholders offer(s) and sell(s) securities, we or the selling stockholders will provide a prospectus supplement to this prospectus that contains specific information about the securities being offered and sold and the specific terms of that offering. The prospectus supplement may also add, update, or change information contained in this prospectus with respect to that offering. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement, you should rely on the prospectus supplement. Before purchasing any securities, you should carefully read both this prospectus and the applicable prospectus supplement, together with the additional information described under the heading “Where You Can Find More Information; Incorporation by Reference.”

Neither we nor the selling stockholders have authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We will not make an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus and the applicable prospectus supplement to this prospectus is accurate as of the date on its respective cover, and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, unless we indicate otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates.

When we refer to “Castellum,” “we,” “our,” “us,” and the “Company” in this prospectus, we mean Castellum, Inc., unless otherwise specified. When we refer to “you,” we mean the holders of the applicable series of securities.

This prospectus may not be used to consummate a sale of securities unless it is accompanied by a prospectus supplement

AVAILABLE INFORMATION

Our website address is www.castellumus.com. The information on our website, however, is not, and should not be deemed to be, a part of this prospectus.

OUR COMPANY

Our Company

Corporate Information

The Company was incorporated in Nevada on September 30, 2010 under the name Passionate Pet, Inc. and in January 2013, the Company changed its name to Firstin Wireless Technology, Inc. In March 2015, the Company changed its name to BioNovelus, Inc. On June 12, 2019, the Company acquired Bayberry Acquisition Corporation, a Nevada corporation (“Bayberry” and, as context requires, the “Bayberry Acquisition”). On February 23, 2021, Bayberry was dissolved with the Nevada Secretary of State as it was non-operational after the merger with the Company. On November 21, 2019, we acquired Corvus Consulting, LLC, (“Corvus”), a Virginia limited liability company. On December 26, 2019, following our acquisition of Corvus, we changed our name from BioNovelus, Inc. to Castellum, Inc.

RISK FACTORS

Investing in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should carefully consider the risk factors we describe in any prospectus supplement and in any related free writing prospectus for a specific offering of securities, as well as those incorporated by reference into this prospectus and any prospectus supplement. You should also carefully consider other information contained and incorporated by reference in this prospectus and any applicable prospectus supplement, including our financial statements and the related notes thereto incorporated by reference in this prospectus. The risks and uncertainties described in the applicable prospectus supplement and our other filings with the SEC incorporated by reference herein are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently consider immaterial may also adversely affect us. If any of the described risks occur, our business, financial condition, or results of operations could be materially harmed. In such case, the value of our securities could decline and you may lose all or part of your investment.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING INFORMATION

This prospectus and the documents incorporated by reference herein contain or may contain forward looking statements that involve risks and uncertainties. All statements other than statements of historical fact contained in this prospectus, including statements regarding future events, our future financial performance, business strategy and plans and objectives of management for future operations, are forward-looking statements. We have attempted to identify forward-looking statements by terminology including “anticipates,” “believes,” “can,” “continue,” “could,” “estimates,” “expects,” “intends,” “may,” “plans,” “potential,” “predicts,” “should,” or “will” or the negative of these terms or other comparable terminology. Although we do not make forward looking statements unless we believe we have a reasonable basis for doing so, we cannot guarantee their accuracy. These statements are only predictions and involve known and unknown risks, uncertainties and other factors, including the risks outlined under “Risk Factors” or elsewhere in this prospectus, which may cause our or our industry’s actual results, levels of activity, performance or achievements expressed or implied by these forward-looking statements.

USE OF PROCEEDS

We intend to use the net proceeds from the sale of the securities as set forth in the applicable prospectus supplement.

DIVIDEND POLICY

DESCRIPTION OF CAPITAL STOCK

The following description of our capital stock is not complete and may not contain all the information you should consider before investing in our capital stock. This description is summarized from, and qualified in its entirety by reference to, our Articles of Incorporation, as amended and Bylaws, as amended which have been publicly filed with the SEC. See “Where You Can Find More Information; Incorporation by Reference.”

Description of Common Stock

The Company is authorized to issue 3,050,000,000 shares of capital stock, par value $0.0001 per share, of which 3,000,000,000 are shares of Common Stock and 50,000,000 are shares of preferred stock. As of November 30, 2023, there were 47,672,427 shares of Common Stock issued and outstanding.

Each share of our Common Stock entitles its holder to one vote in the election of each director and on all other matters voted on generally by our stockholders, other than any matter that (1) solely relates to the terms of any outstanding series of preferred stock or the number of shares of that series and (2) does not affect the number of authorized shares of preferred stock or the powers, privileges, and rights pertaining to the Common Stock. No share of our Common Stock affords any cumulative voting rights. This means that the holders of a majority of the voting power of the shares voting for the election of directors can elect all directors to be elected if they choose to do so.

Holders of our Common Stock will be entitled to dividends in such amounts and at such times as our Board of Directors in its discretion may declare out of funds legally available for the payment of dividends. We currently intend to retain our entire available discretionary cash flow to finance the growth, development, and expansion of our business and do not anticipate paying any cash dividends on the Common Stock in the foreseeable future. Any future dividends will be paid at the discretion of our Board of Directors.

If we liquidate or dissolve our business, the holders of our Common Stock will share ratably in all our assets that are available for distribution to our stockholders after our creditors are paid in full and the holders of all series of our outstanding preferred stock, if any, receive their liquidation preferences in full.

Our Common Stock has no preemptive rights and is not convertible or redeemable or entitled to the benefits of any sinking or repurchase fund.

The Common Stock is listed on the NYSE American under the trading symbol “CTM.”

The Company’s transfer agent is Nevada Agency and Transfer Company with an address at 50 West Liberty Street, Suite 880, Reno, NV 89501 and a phone number of (775) 322-0626.

Anti-Takeover Provisions

Business Combinations

The “business combination” provisions of Sections 78.411 to 78.444, inclusive, of the Nevada Revised Statutes, or NRS, generally prohibit a Nevada corporation with at least 200 stockholders of record, a “resident domestic corporation,” from engaging in various “combination” transactions with any “interested stockholder” unless certain conditions are met or the corporation has elected in its articles of incorporation to not be subject to these provisions. We have not elected to opt out of these provisions and if we meet the definition of resident domestic corporation, now or in the future, our company will be subject to these provisions.

A “combination” is generally defined to include (a) a merger or consolidation of the resident domestic corporation or any subsidiary of the resident domestic corporation with the interested stockholder or affiliate or associate of the interested stockholder; (b) any sale, lease, exchange, mortgage, pledge, transfer, or other disposition, in one transaction or a series of transactions, by the resident domestic corporation or any subsidiary of the resident domestic corporation to or with the interested stockholder or affiliate or associate of the interested stockholder having: (i) an aggregate market value equal to 5% or more of the aggregate market value of the assets of the resident domestic corporation, (ii) an aggregate market value equal to 5% or more of the aggregate market value of all outstanding shares of the resident domestic corporation, or (iii) 10% or more of the earning power or net income of

the resident domestic corporation; (c) the issuance or transfer in one transaction or series of transactions of shares of the resident domestic corporation or any subsidiary of the resident domestic corporation having an aggregate market value equal to 5% or more of the resident domestic corporation to the interested stockholder or affiliate or associate of the interested stockholder; and (d) certain other transactions with an interested stockholder or affiliate or associate of the interested stockholder.

An “interested stockholder” is generally defined as a person who, together with affiliates and associates, owns (or within two years, did own) 10% or more of a corporation’s voting stock. An “affiliate” of the interested stockholder is any person that directly or indirectly through one or more intermediaries is controlled by or is under common control with the interested stockholder. An “associate” of an interested stockholder is any (a) corporation or organization of which the interested stockholder is an officer or partner or is directly or indirectly the beneficial owner of 10% or more of any class of voting shares of such corporation or organization; (b) trust or other estate in which the interested stockholder has a substantial beneficial interest or as to which the interested stockholder serves as trustee or in a similar fiduciary capacity; or (c) relative or spouse of the interested stockholder, or any relative of the spouse of the interested stockholder, who has the same home as the interested stockholder.

If applicable, the prohibition is for a period of two years after the date of the transaction in which the person became an interested stockholder, unless such transaction is approved by the board of directors prior to the date the interested stockholder obtained such status; or the combination is approved by the board of directors and thereafter is approved at a meeting of the stockholders by the affirmative vote of stockholders representing at least 60% of the outstanding voting power held by disinterested stockholders; and extends beyond the expiration of the two-year period, unless (a) the combination was approved by the board of directors prior to the person becoming an interested stockholder; (b) the transaction by which the person first became an interested stockholder was approved by the board of directors before the person became an interested stockholder; (c) the transaction is approved by the affirmative vote of a majority of the voting power held by disinterested stockholders at a meeting called for that purpose no earlier than two years after the date the person first became an interested stockholder; or (d) if the consideration to be paid to all stockholders other than the interested stockholder is, generally, at least equal to the highest of: (i) the highest price per share paid by the interested stockholder within the three years immediately preceding the date of the announcement of the combination or in the transaction in which it became an interested stockholder, whichever is higher, plus compounded interest and less dividends paid, (ii) the market value per share of common shares on the date of announcement of the combination and the date the interested stockholder acquired the shares, whichever is higher, plus compounded interest and less dividends paid, or (iii) for holders of preferred stock, the highest liquidation value of the preferred stock, plus accrued dividends, if not included in the liquidation value. With respect to (i) and (ii) above, the interest is compounded at the rate for one-year United States Treasury obligations from time to time in effect.

Applicability of the Nevada business combination statute would discourage parties interested in taking control of our company if they cannot obtain the approval of our Board. These provisions could prohibit or delay a merger or other takeover or change in control attempt and, accordingly, may discourage attempts to acquire our company even though such a transaction may offer our stockholders the opportunity to sell their stock at a price above the prevailing market price.

Control Share Acquisitions

The “control share” provisions of Sections 78.378 to 78.3793, inclusive, of the NRS, apply to “issuing corporations” that are Nevada corporations with at least 200 stockholders of record, including at least 100 stockholders of record who are Nevada residents, and that conduct business directly or indirectly in Nevada, unless the corporation has elected to not be subject to these provisions.

The control share statute prohibits an acquirer of shares of an issuing corporation, under certain circumstances, from voting its shares of a corporation’s stock after crossing certain ownership threshold percentages, unless the acquirer obtains approval of the target corporation’s disinterested stockholders. The statute specifies three thresholds: (a) one-fifth or more but less than one-third, (b) one-third but less than a majority, and (c) a majority or more, of the outstanding voting power. Generally, once a person acquires shares in excess of any of the thresholds, those shares and any additional shares acquired within 90 days thereof become “control shares” and such control

shares are deprived of the right to vote until disinterested stockholders restore the right. These provisions also provide that if control shares are accorded full voting rights and the acquiring person has acquired a majority or more of all voting power, all other stockholders who do not vote in favor of authorizing voting rights to the control shares are entitled to demand payment for the fair value of their shares in accordance with statutory procedures established for dissenters’ rights.

A corporation may elect to not be governed by, or “opt out” of, the control shares provisions by making an election in its articles of incorporation or bylaws, provided that the opt-out election must be in place on the 10th day following the date an acquiring person has acquired a controlling interest, that is, crossing any of the three thresholds described above. We have not opted out of these provisions and will be subject to the control share provisions of the NRS if we meet the definition of an issuing corporation upon an acquiring person acquiring a controlling interest unless we later opt out of these provisions and the opt out is in effect on the 10th day following such occurrence.

The effect of the Nevada control share statute is that the acquiring person, and those acting in association with the acquiring person, will obtain only such voting rights in the control shares as are conferred by a resolution of the stockholders at an annual or special meeting. The Nevada control share law, if applicable, could have the effect of discouraging takeovers of our company.

DESCRIPTION OF PREFERRED STOCK

Our Articles of Incorporation empowers our board of directors, without action by our shareholders, to issue up to 50,000,000 shares of preferred stock. The Company has designated a total of 30,000,000 shares of preferred stock in the form of Series A Preferred Stock, Series B Preferred Stock, and Series C Preferred Stock. The board may, without action by our shareholders, from time to time, issue up to 20,000,000 more shares of preferred stock in one or more series, which preferred stock may be offered by this prospectus and supplements thereto.

Series A Preferred Stock

The Company has designated 10,000,000 shares of Series A Preferred Stock, par value of $0.0001. As of November 30, 2023, the Company has 5,875,000 shares of Series A Preferred Stock issued and outstanding, which is convertible into 587,500 shares of Common Stock. The holders of our Series A Preferred Stock are entitled to vote on an as-converted basis. Holders of the Series A preferred stock are entitled to receive a dividend of $0.0125 per year, one-twelfth of which shall be payable each calendar month. The Series A preferred stock may be redeemed at the Company’s option at $1 per share at any time upon 30 days advanced written notice. Holders of Series A preferred stock are entitled to receive liquidation preference pari passu with the holders of Series B preferred stock and Series C preferred stock and prior to and in preference to any distribution of any of the assets of the Company to the holders of common stock.

Series B Preferred Stock

The Company has designated 10,000,000 shares of Series B Preferred Stock, par value of $0.0001. As of November 30, 2023, the Company has 0 shares of Series B Preferred Stock issued and outstanding.

Series C Preferred Stock

The Company has designated 10,000,000 shares of Series C Preferred Stock, par value of $0.0001. As of November 30, 2023, the Company has 770,000 shares of Series C Preferred Stock issued and outstanding, which are convertible into 481,250 shares of the Company's common stock. The holders of our Series C Preferred Stock are entitled to vote on an as-converted basis. The Series C preferred stock has a stated value of $1. Holders of the Series C preferred stock are entitled to receive a dividend of $0.06 per year. Holders of the Series C preferred stock received two shares of common stock of the Company for every one share of Series C preferred stock issued. At any time after July 16, 2028 the Company has the right to redeem all of the issued and outstanding shares of Series C preferred stock at a redemption price per preferred share equal to the stated value of $1. The Series C preferred stock has no maturity date or scheduled redemption date. There is no sinking fund provisions applicable to the Series C preferred stock. Holders of the Series C preferred stock are entitled to receive liquidation preference, pari passu with the holders of Series A preferred stock and Series B preferred stock and prior to and in preference to any distribution of any of the assets of the Company to the holders of common stock.

We will fix the rights, preferences, privileges, and restrictions of the preferred stock of each series in the certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part or will incorporate by reference from a current report on Form 8-K that we file with the SEC, the form of any certificate of designation that describes the terms of the series of preferred stock we are offering before the issuance of the related series of preferred stock. This description will include any or all of the following, as required:

•the title and stated value;

•the number of shares we are offering;

•the liquidation preference per share;

•the purchase price;

•the dividend rate, period, and payment date and method of calculation for dividends;

•whether dividends will be cumulative or non-cumulative and, if cumulative, the date from which dividends will accumulate;

•any contractual limitations on our ability to declare, set aside, or pay any dividends;

•the procedures for any auction and remarketing, if any;

•the provisions for a sinking fund, if any;

•the provisions for redemption or repurchase, if applicable, and any restrictions on our ability to exercise those redemption and repurchase rights;

•any listing of the preferred stock on any securities exchange or market;

•whether the preferred stock will be convertible into our common stock, and, if applicable, the conversion price, or how it will be calculated, and the conversion period;

•voting rights, if any, of the preferred stock;

•preemptive rights, if any;

•restrictions on transfer, sale or other assignment, if any;

•whether interests in the preferred stock will be represented by depositary shares;

•a discussion of any material or special United States federal income tax considerations applicable to the preferred stock;

•the relative ranking and preferences of the preferred stock as to dividend rights and rights if we liquidate, dissolve , or wind up our affairs;

•any limitations on issuance of any class or series of preferred stock ranking senior to or on a parity with the series of preferred stock as to dividend rights and rights if we liquidate, dissolve, or wind up our affairs; and

•any other specific terms, preferences, rights or limitations of, or restrictions on, the preferred stock.

If we issue shares of preferred stock under this prospectus, after receipt of payment therefor, the shares will be fully paid and non-assessable.

The Nevada Revised Statues provide that the holders of preferred stock will have the right to vote separately as a class on any proposal involving fundamental changes in the rights of holders of that preferred stock. This right is in addition to any voting rights provided for in the applicable certificate of designation.

Our board of directors may authorize the issuance of preferred stock with voting or conversion rights that could adversely affect the voting power or other rights of the holders of our common stock. Preferred stock could be issued quickly with terms designed to delay or prevent a change in control of our Company or make removal of management more difficult. Additionally, the issuance of preferred stock could have the effect of decreasing the market price of our common stock.

DESCRIPTION OF WARRANTS

We may offer to sell warrants from time to time. If we do so, we will describe the specific terms of the warrants in a prospectus supplement. In particular, we may issue warrants for the purchase of Common Stock or preferred stock in one or more series. We may also issue warrants independently or together with other securities and the warrants may be attached to or separate from those securities.

We will evidence each series of warrants by warrant certificates that we will issue under a separate agreement. We will enter into the warrant agreement with a warrant agent. We will indicate the name and address of the warrant agent in the applicable prospectus supplement relating to a particular series of warrants.

We will describe in the applicable prospectus supplement the terms of the series of warrants, including:

•the offering price and aggregate number of warrants offered;

•the currency for which the warrants may be purchased;

•if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each such security or each principal amount of such security;

•if applicable, the date on and after which the warrants and the related securities will be separately transferable;

•in the case of warrants to purchase Common Stock or preferred stock, the number of shares of Common Stock or preferred stock, as the case may be, purchasable upon the exercise of one warrant and the price at which these shares may be purchased upon such exercise;

•the effect of any merger, consolidation, sale, or other disposition of our business on the warrant agreement and the warrants;

•the terms of any rights to redeem or call the warrants;

•any provisions for changes to or adjustments in the exercise price or number of securities issuable upon exercise of the warrants;

•the dates on which the right to exercise the warrants will commence and expire;

•the manner in which the warrant agreement and warrants may be modified;

•certain United States federal income tax consequences of holding or exercising the warrants;

•the terms of the securities issuable upon exercise of the warrants; and

•any other specific material terms, preferences, rights, or limitations of or restrictions on the warrants.

Holders may exercise the warrants by delivering the warrant certificate representing the warrants to be exercised together with other requested information, and paying the required amount to the warrant agent in immediately available funds, as provided in the applicable prospectus supplement. We will set forth in the applicable prospectus supplement the information that the holder of the warrant will be required to deliver to the warrant agent.

Upon receipt of the required payment and the warrant certificate properly completed and duly executed at the office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will issue and deliver the securities purchasable upon such exercise. If a holder exercises fewer than all of the warrants represented by the warrant certificate, then we will issue a new warrant certificate for the remaining amount of warrants.

Holders will not have any of the rights of the holders of the securities purchasable upon the exercise of warrants until you exercise them. Accordingly, holders will not be entitled to, among other things, vote or receive dividend payments or similar distributions on the securities you can purchase upon exercise of the warrants.

The information provided above is only a summary of the terms under which we may offer warrants for sale. Accordingly, investors must carefully review the applicable warrant agreement for more information about the specific terms and conditions of these warrants before investing in us. In addition, please carefully review the information provided in the applicable prospectus supplement, which contains additional information that is important for you to consider in evaluating an investment in our securities.

DESCRIPTION OF RIGHTS

We may issue rights to our stockholders to purchase shares of our Common Stock or preferred stock described in this prospectus. We may offer rights separately or together with one or more additional rights, preferred stock, Common Stock, warrants, or any combination of those securities in the form of units, as described in the applicable prospectus supplement. Each series of rights will be issued under a separate rights agreement to be entered into between us and a bank or trust company, as rights agent. The rights agent for any rights we offer will be set forth in the applicable prospectus supplement. The rights agent will act solely as our agent in connection with the certificates relating to the rights of the series of certificates and will not assume any obligation or relationship of agency or trust for or with any holders of rights certificates or beneficial owners of rights. The following description sets forth certain general terms and provisions of the rights to which any prospectus supplement may relate. The particular terms of the rights to which any prospectus supplement may relate and the extent, if any, to which the general provisions may apply to the rights so offered will be described in the applicable prospectus supplement. To the extent that any particular terms of the rights, rights agreement, or rights certificates described in a prospectus supplement differ from any of the terms described below, then the terms described below will be deemed to have been superseded by that prospectus supplement. We encourage you to read the applicable rights agreement and rights certificate for additional information before you decide whether to purchase any of our rights.

The prospectus supplement relating to any rights that we offer will include specific terms relating to the offering, including, among other matters:

•the date of determining the stockholders entitled to the rights distribution;

•the aggregate number of shares of Common Stock, preferred stock, or other securities purchasable upon exercise of the rights;

•the exercise price;

•the aggregate number of rights issued;

•whether the rights are transferrable and the date, if any, on and after which the rights may be separately transferred;

•the date on which the right to exercise the rights will commence, and the date on which the right to exercise the rights will expire;

•the method by which holders of rights will be entitled to exercise;

•the conditions to the completion of the offering;

•the withdrawal, termination, and cancellation rights;

•whether there are any backstop or standby purchaser or purchasers and the terms of their commitment;

•whether stockholders are entitled to oversubscription rights;

•any U.S. federal income tax considerations; and

•any other terms of the rights, including terms, procedures, and limitations relating to the distribution, exchange, and exercise of the rights.

If less than all of the rights issued in any rights offering are exercised, we may offer any unsubscribed securities directly to persons other than stockholders, to or through agents, underwriters, or dealers or through a combination of such methods, including pursuant to standby arrangements, as described in the applicable prospectus supplement. In connection with any rights offering, we may enter into a standby underwriting or other arrangement with one or more underwriters or other persons pursuant to which such underwriters or other persons would purchase any offered securities remaining unsubscribed for after such rights offering.

DESCRIPTION OF UNITS

We may issue units consisting of any combination of the other types of securities offered under this prospectus in one or more series. We may evidence each series of units by unit certificates that we will issue under a separate agreement. We may enter into unit agreements with a unit agent. We will indicate the name and address of the unit agent in the applicable prospectus supplement relating to a particular series of units.

The following description, together with the additional information included in any applicable prospectus supplement, summarizes the general features of the units that we may offer under this prospectus. You should read any prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the series of units being offered, as well as the complete unit agreements that contain the terms of the units. Specific unit agreements will contain additional important terms and provisions and we will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from another report that we file with the SEC, the form of each unit agreement relating to units offered under this prospectus.

If we offer any units, certain terms of that series of units will be described in the applicable prospectus supplement, including, without limitation, the following, as applicable:

•the title of the series of units;

•identification and description of the separate constituent securities comprising the units;

•the price or prices at which the units will be issued;

•the date, if any, on and after which the constituent securities comprising the units will be separately transferable;

•a discussion of certain United States federal income tax considerations applicable to the units; and

•any other terms of the units and their constituent securities.

LEGAL OWNERSHIP OF SECURITIES

We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee, depositary or warrant agent maintain for this purpose as the “holders” of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as “indirect holders” of those securities. As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

Book-Entry Holders

We may issue securities in book-entry form only, as we will specify in any applicable prospectus supplement. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depositary on behalf of other financial institutions that participate in the depositary’s book-entry system. These participating institutions, which are referred to as participants, in turn, hold beneficial interests in the securities on behalf of themselves or their customers.

Only the person in whose name a security is registered is recognized as the holder of that security. Securities issued in global form will be registered in the name of the depositary or its participants. Consequently, for securities issued in global form, we will recognize only the depositary as the holder of the securities, and we will make all payments on the securities to the depositary. The depositary passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depositary and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

As a result, investors in a global security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depositary’s book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not legal holders, of the securities.

Street Name Holders

We may terminate a global security or issue securities in non-global form. In these cases, investors may choose to hold their securities in their own names or in “street name.” Securities held by an investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

For securities held in street name, we or any applicable trustee or depositary will recognize only the intermediary banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we or any applicable trustee or depositary will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not holders, of those securities.

Legal Holders

Our obligations, as well as the obligations of any applicable trustee and of any third parties employed by us or a trustee, run only to the legal holders of the securities. We do not have obligations to investors who hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

For example, once we make a payment or give a notice to the legal holder, we have no further responsibility for the payment or notice even if that legal holder is required, under agreements with its participants or customers or by

law, to pass it along to the indirect holders but does not do so. Whether and how the legal holders contact the indirect holders is up to the legal holders.

Special Considerations for Indirect Holders

If you hold securities through a bank, broker or other financial institution, either in book-entry form because the securities are represented by one or more global securities or in street name, you should check with your own institution to find out:

•how it handles securities payments and notices;

•whether it imposes fees or charges;

•how it would handle a request for the holder’s consent, if ever required;

•whether and how you can instruct it to send you securities registered in your own name so you can be a holder, if that is permitted in the future;

•how it would exercise rights under the securities if there were a default or other event triggering the need for holders to act to protect their interests; and

•if the securities are in book-entry form, how the depositary’s rules and procedures will affect these matters.

Global Securities

A global security is a security that represents one or any other number of individual securities held by a depositary. Generally, all securities represented by the same global securities will have the same terms.

Each security issued in book-entry form will be represented by a global security that we issue to, deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depositary. Unless we specify otherwise in any applicable prospectus supplement, DTC will be the depositary for all securities issued in book-entry form.

A global security may not be transferred to or registered in the name of anyone other than the depositary, its nominee or a successor depositary, unless special termination situations arise. We describe those situations below under “Special Situations When a Global Security Will Be Terminated.” As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and legal holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by means of an account with a broker, bank or other financial institution that in turn has an account with the depositary or with another institution that does. Thus, an investor whose security is represented by a global security will not be a legal holder of the security, but only an indirect holder of a beneficial interest in the global security.

If the prospectus supplement for a particular security indicates that the security will be issued in global form only, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

Special Considerations for Global Securities

The rights of an indirect holder relating to a global security will be governed by the account rules of the investor’s financial institution and of the depositary, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a holder of securities and instead deal only with the depositary that holds the global security.

If securities are issued only in the form of a global security, an investor should be aware of the following:

•an investor cannot cause the securities to be registered in his or her name, and cannot obtain non-global certificates for his or her interest in the securities, except in the special situations we describe below;

•an investor will be an indirect holder and must look to his or her own bank, broker or other financial institution for payments on the securities and protection of his or her legal rights relating to the securities, as we describe above;

•an investor may not be able to sell interests in the securities to some insurance companies and to other institutions that are required by law to own their securities in non-book-entry form;

•an investor may not be able to pledge his or her interest in a global security in circumstances where certificates representing the securities must be delivered to the lender or other beneficiary of the pledge in order for the pledge to be effective;

•the depositary’s policies, which may change from time to time, will govern payments, transfers, exchanges and other matters relating to an investor’s interest in a global security;

•we and any applicable trustee have no responsibility for any aspect of the depositary’s actions or for its records of ownership interests in a global security, nor do we or any applicable trustee supervise the depositary in any way;

•the depositary may, and we understand that DTC will, require that those who purchase and sell interests in a global security within its book-entry system use immediately available funds, and your bank, broker or other financial institution may require you to do so as well; and

•financial institutions that participate in the depositary’s book-entry system, and through which an investor holds its interest in a global security, may also have their own policies affecting payments, notices and other matters relating to the securities.

There may be more than one financial intermediary in the chain of ownership for an investor. We do not monitor and are not responsible for the actions of any of those intermediaries.

Special Situations When a Global Security Will Be Terminated

In a few special situations described below, the global security will terminate and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult their own banks, brokers or other financial institutions to find out how to have their interests in securities transferred to their own name, so that they will be direct holders. We have described the rights of holders and street name investors above.

Unless we provide otherwise in any applicable prospectus supplement, the global security will terminate when the following special situations occur:

•if the depositary notifies us that it is unwilling, unable or no longer qualified to continue as depositary for that global security and we do not appoint another institution to act as depositary within 90 days;

•if we notify any applicable trustee that we wish to terminate that global security; or

•if an event of default has occurred with regard to securities represented by that global security and has not been cured or waived.

The prospectus supplement may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by any applicable prospectus supplement. When a global security terminates, the depositary, and not we or any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

PLAN OF DISTRIBUTION

We may sell the securities from time to time pursuant to underwritten public offerings, negotiated transactions, block trades or a combination of these methods. We may sell the securities to or through underwriters or dealers, through agents, or directly to one or more purchasers. We may distribute securities from time to time in one or more transactions:

•at a fixed price or prices, which may be changed;

•at market prices prevailing at the time of sale;

•at prices related to such prevailing market prices; or

•at negotiated prices.

We may also sell equity securities covered by this registration statement in an “at the market” offering as defined in Rule 415(a)(4) under the Securities Act. Such offering may be made into an existing trading market for such securities in transactions at other than a fixed price on or through the facilities of the NYSE American or any other securities exchange or quotation or trading service on which such securities may be listed, quoted or traded at the time of sale.

Such at the market offerings, if any, may be conducted by underwriters acting as principal or agent.

A prospectus supplement or supplements (and any related free writing prospectus that we may authorize to be provided to you) will describe the terms of the offering of the securities, including, to the extent applicable:

•the name or names of any underwriters, dealers or agents, if any;

•the purchase price of the securities and the proceeds we will receive from the sale;

•any over-allotment options under which underwriters may purchase additional securities from us;

•any agency fees or underwriting discounts and other items constituting agents’ or underwriters’ compensation;

•any public offering price;

•any discounts or concessions allowed or reallowed or paid to dealers; and

•any securities exchange or market on which the securities may be listed.

Only underwriters named in the prospectus supplement are underwriters of the securities offered by the prospectus supplement.

If underwriters are used in the sale, they will acquire the securities for their own account and may resell the securities from time to time in one or more transactions at a fixed public offering price or at varying prices determined at the time of sale. The obligations of the underwriters to purchase the securities will be subject to the conditions set forth in the applicable underwriting agreement. We may offer the securities to the public through underwriting syndicates represented by managing underwriters or by underwriters without a syndicate. Subject to certain conditions, the underwriters will be obligated to purchase all of the securities offered by the prospectus supplement. Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may change from time to time. We may use underwriters with whom we have a material relationship. We will describe in the prospectus supplement, naming the underwriter, the nature of any such relationship.

We may sell securities directly or through agents we designate from time to time. We will name any agent involved in the offering and sale of securities, and we will describe any commissions we will pay the agent in the prospectus supplement. Unless the prospectus supplement states otherwise, our agent will act on a best-efforts basis for the period of its appointment.

We may authorize agents or underwriters to solicit offers by certain types of institutional investors to purchase securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. We will describe the conditions to these contracts and the commissions we must pay for solicitation of these contracts in the prospectus supplement.

We may provide agents and underwriters with indemnification against civil liabilities related to this offering, including liabilities under the Securities Act, or contribution with respect to payments that the agents or underwriters may make with respect to these liabilities. Agents and underwriters may engage in transactions with, or perform services for, us in the ordinary course of business.

All securities we offer, other than common stock or our publicly-traded warrants, will be new issues of securities with no established trading market. Any underwriters may make a market in these securities, but will not be obligated to do so and may discontinue any market making at any time without notice. We cannot guarantee the liquidity of the trading markets for any securities.

Any underwriter may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids. Overallotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum. Short covering transactions involve purchases of the securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a stabilizing or covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time. These transactions may be effected on any exchange or over-the-counter market or otherwise.

Underwriters may engage in passive market making transactions in the securities in accordance with Regulation M. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security; if all independent bids are lowered below the passive market maker’s bid, however, the passive market maker’s bid must then be lowered when certain purchase limits are exceeded. Passive market making may stabilize the market price of the securities at a level above that which might otherwise prevail in the open market and, if commenced, may be discontinued at any time.

LEGAL MATTERS

Lucosky Brookman LLP, will pass upon certain legal matters relating to the issuance and sale of the common stock, preferred stock, warrants and units offered hereby on behalf of Castellum, Inc. Additional legal matters may be passed upon for us or any underwriters, dealers or agents, by counsel that we will name in the applicable prospectus supplement.

EXPERTS

Our consolidated financial statements as of December 31, 2022 and 2021 and for each of the years in the two-year period ended December 31, 2022 incorporated in this Prospectus by reference from the Company’s Annual Report on From 10-K for the year ended December 31, 2022 have been audited by RSM US LLP, an independent registered public accounting firm, as stated in their reports thereon, incorporated herein by reference,and have been incorporated in this Prospectus and Registration Statement in reliance upon such report and upon the authority of such firm as experts in accounting and auditing.

INFORMATION INCORPORATED BY REFERENCE

•Our Annual Report on Form 10-K for the year ended December 31, 2022, filed with the SEC on March 17, 2023;

•Our Quarterly Report on Form 10-Q for the period ended March 31, 2023, filed with the SEC on May 15, 2023

•Our Quarterly Report on Form 10-Q for the period ended June 30, 2023, filed with the SEC on August 14, 2023;

•Our Quarterly Report on Form 10-Q for the period ended September 30, 2023, filed with the SEC on November 14, 2023;