PROSPECTUS SUPPLEMENT NO. 4 (TO PROSPECTUS DATED JUNE 23, 2020) Filed Pursuant to Rule 424(b)(3) Registration Nos. 333-238990 and 333-239399

51,400,000 Units consisting of

Common Shares or Pre-Funded Warrants to Purchase Common Shares

and Class A Warrants to Purchase Common Shares

This is a supplement (“Prospectus Supplement”) to the prospectus, dated June 23, 2020 (“Prospectus”) of Castor Maritime Inc. (the “Company”), which forms a part of the Company’s Registration Statement on Form F-1 (Registration Nos. 333-238990 and 333-239399), as amended or supplemented from time to time.

On July 29, 2020, the Company filed a Current Report on Form 6-K (the “Form 6-K”) with the U.S. Securities and Exchange Commission (the “Commission”) as set forth below.

This Prospectus Supplement should be read in conjunction with, and delivered with, the Prospectus and is qualified by reference to the Prospectus except to the extent that the information in this Prospectus Supplement supersedes the information contained in the Prospectus.

This Prospectus Supplement is not complete without, and may not be delivered or utilized except in connection with, the Prospectus, including any amendments or supplements to it.

Investing in our securities involves a high degree of risk. See “Risk Factors” beginning on page 12 of the Prospectus for a discussion of information that should be considered in connection with an investment in our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is July 29, 2020.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13A-16 OR 15D-16 OF

THE SECURITIES EXCHANGE ACT OF 1934

For the month of July 2020

Commission File Number: 001-38802

 CASTOR MARITIME INC.

(Translation of registrant’s name into English)

223 Christodoulou Chatzipavlou Street, Hawaii Royal Gardens, 3036 Limassol, Cyprus

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F  ⌧           Form 40-F  ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ☐

Note: Regulation S-T Rule 101(b) (1) only permits the submission in paper of a Form 6-K if submitted solely to provide an attached annual report to security holders.

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ☐

Note: Regulation S-T Rule 101(b)(7) only permits the submission in paper of a Form 6-K if submitted to furnish a report or other document that the registrant foreign private issuer must furnish and make public under the laws of the jurisdiction in which the registrant is incorporated, domiciled or legally organized (the registrant’s “home country”), or under the rules of the home country exchange on which the registrant’s securities are traded, as long as the report or other document is not a press release, is not required to be and has not been distributed to the registrant’s security holders, and, if discussing a material event, has already been the subject of a Form 6-K submission or other Commission filing on EDGAR.

INFORMATION CONTAINED IN THIS FORM 6-K REPORT

Attached to this report on Form 6-K as Exhibit 99.1 is a copy of the press release issued by Castor Maritime Inc. (the “Company”) on July 29, 2020, reporting that the Company, through a separate wholly-owned subsidiary, entered into an agreement to purchase a 2010 Japanese built Panamax dry bulk carrier for a purchase price of $12.75 million from an unaffiliated third party.

Except for the commentary of Petros Panagiotidis, the information contained in this report on Form 6-K and the exhibit attached hereto are hereby incorporated by reference into the Company's registration statement on Form F-3 (File No. 333-232052) that was filed with the SEC on June 10, 2019 and declared effective on June 21, 2019.

SIGNATURES

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

	CASTOR MARITIME INC.
Dated: July 29, 2020	By:	/s/ Petros Panagiotidis
		Petros Panagiotidis Chairman, Chief Executive Officer and Chief Financial Officer

Exhibit 99.1

Castor Maritime Inc. Announces Vessel Acquisition

Limassol, Cyprus, July 29, 2020 – Castor Maritime Inc. (NASDAQ: CTRM), (“Castor” or the “Company”), a global shipping company specializing in the ownership of dry bulk vessels, announces that yesterday it entered, through a separate wholly-owned subsidiary, into an agreement to purchase a 2010 Japan-built Panamax dry bulk carrier for a purchase price of $12.75 million from an unaffiliated third party seller.

The acquisition is expected to be consummated by taking delivery of the vessel sometime in the end of the third quarter / beginning of the fourth quarter of this year and is subject to the satisfaction of certain customary closing conditions.

Petros Panagiotidis, Chairman, Chief Executive Officer and Chief Financial Officer of Castor, commented:

“We are very pleased that we have been able to utilize further our recently raised capital by agreeing the acquisition of our fifth vessel, in a very short time since the acquisition of our fourth. We are making swift progress on our expansion and renewal plan that we set in place last year and are actively continuing to assess the various opportunities presented to us. Our key goal continues to be the further expansion of our fleet and the deployment of our readily available liquidity in the most prudent and favorable way for our shareholders.”

About Castor Maritime Inc.

Castor Maritime Inc. is an international provider of shipping transportation services through its ownership of dry bulk vessels. The Company’s vessels are employed primarily on medium-term charters and transport a range of dry bulk cargoes, including such commodities as coal, grain and other materials along worldwide shipping routes.

Upon completion of this acquisition, the Company's fleet will consist of five Panamax dry bulk carriers.

For more information please visit the company’s website at www.castormaritime.com

Cautionary Statement Regarding Forward-Looking Statements

Matters discussed in this press release may constitute forward-looking statements. The Private Securities Litigation Reform Act of 1995 provides safe harbor protections for forward-looking statements in order to encourage companies to provide prospective information about their business. Forward-looking statements include statements concerning plans, objectives, goals, strategies, future events or performance, and underlying assumptions and other statements, which are other than statements of historical facts. The Company desires to take advantage of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 and is including this cautionary statement in connection with this safe harbor legislation. The words “believe,” “anticipate,” “intend,” “estimate,” “forecast,” “project,” “plan,” “potential,” “will,” “may,” “should,” “expect,” “pending” and similar expressions identify forward-looking statements. The forward-looking statements in this press release are based upon various assumptions, many of which are based, in turn, upon further assumptions, including without limitation, our management’s examination of historical operating trends, data contained in our records and other data available from third parties. Although we believe that these assumptions were reasonable when made, because these assumptions are inherently subject to significant uncertainties and contingencies which are difficult or impossible to predict and are beyond our control, we cannot assure you that we will achieve or accomplish these expectations, beliefs or projections. We undertake no obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise. In addition to these important factors, other important factors that, in the Company’s view, could cause actual results to differ materially from those discussed in the forward‐looking statements include general dry bulk shipping market conditions, including fluctuations in charterhire rates and vessel values, the strength of world economies the stability of Europe and the Euro, fluctuations in interest rates and foreign exchange rates, changes in demand in the dry bulk shipping industry, including the market for our vessels, changes in our operating expenses, including bunker prices, dry docking and insurance costs, changes in governmental rules and regulations or actions taken by regulatory authorities, potential liability from pending or future litigation, general domestic and international political conditions, potential disruption of shipping routes due to accidents or political events, the availability of financing and refinancing and grow our business, vessel breakdowns and instances of off‐hire, risks associated with vessel construction, potential exposure or loss from investment in derivative instruments, potential conflicts of interest involving our Chief Executive Officer, his family and other members of our senior management, and our ability to complete acquisition transactions as planned. Please see our filings with the Securities and Exchange Commission for a more complete discussion of these and other risks and uncertainties. The information set forth herein speaks only as of the date hereof, and the Company disclaims any intention or obligation to update any forward‐looking statements as a result of developments occurring after the date of this communication.

CONTACT DETAILS

For further information please contact:

Petros Panagiotidis

Castor Maritime Inc.

Email: info@castormaritime.com

Media Contact:

Kevin Karlis

Capital Link

Email: castormaritime@capitallink.com