Sec Form 3 Filing - Serafini John Sheldon @ HawkEye 360, Inc. - 2026-05-06

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Serafini John Sheldon 2. Issuer Name and Ticker or Trading Symbol HawkEye 360, Inc. [ HAWK] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) President and CEO (Last) (First) (Middle) C/O HAWKEYE 360, INC., 450 SPRINGPARK PLACE, SUITE 500 3. Date of Earliest Transaction (MM/DD/YY) 05/06/2026 (Street) HERNDON, VA20170 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 496,675 ( 1 ) ( 2 ) D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series A-1 Preferred Stock ( 3 ) ( 3 ) ( 3 ) Common Stock 3,181 D Series A-1 Preferred Stock ( 3 ) ( 3 ) ( 3 ) Common Stock 4,545 I See Footnote ( 4 ) Series A-2 Preferred Stock ( 3 ) ( 3 ) ( 3 ) Common Stock 46,569 D Series A-3 Preferred Stock ( 3 ) ( 3 ) ( 3 ) Common Stock 5,010 D Series C Preferred Stock ( 3 ) ( 3 ) ( 3 ) Common Stock 2,686 D Series D Preferred Stock ( 3 ) ( 3 ) ( 3 ) Common Stock 851 D Stock Option (Right to Buy) $ 0.23 ( 5 ) 02/08/2027 Common Stock 233,272 D Stock Option (Right to Buy) $ 0.23 ( 5 ) 02/08/2027 Common Stock 1,171,357 D Stock Option (Right to Buy) $ 0.45 ( 5 ) 03/14/2028 Common Stock 12,668 D Stock Option (Right to Buy) $ 0.77 ( 5 ) 11/26/2028 Common Stock 135,663 D Stock Option (Right to Buy) $ 0.77 ( 5 ) 02/18/2029 Common Stock 10,958 D Stock Option (Right to Buy) $ 2.29 ( 5 ) 09/18/2029 Common Stock 659,000 D Stock Option (Right to Buy) $ 2.64 ( 5 ) 01/26/2031 Common Stock 5,682 D Stock Option (Right to Buy) $ 2.78 ( 5 ) 06/08/2031 Common Stock 284,802 D Stock Option (Right to Buy) $ 2.78 ( 5 ) 06/08/2031 Common Stock 259,882 D Stock Option (Right to Buy) $ 4.25 ( 5 ) 04/19/2032 Common Stock 297,800 D Stock Option (Right to Buy) $ 4.25 ( 5 ) 04/19/2032 Common Stock 271,742 D Stock Option (Right to Buy) $ 2.31 ( 6 ) 10/22/2033 Common Stock 278,460 D Stock Option (Right to Buy) $ 2.31 ( 7 ) 10/22/2033 Common Stock 278,460 D Stock Option (Right to Buy) $ 3.02 ( 5 ) 04/22/2035 Common Stock 72,826 D Stock Option (Right to Buy) $ 11.42 ( 8 ) 02/05/2036 Common Stock 495,000 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Serafini John Sheldon C/O HAWKEYE 360, INC. 450 SPRINGPARK PLACE, SUITE 500 HERNDON, VA20170 X President and CEO Signatures /s/ Michael S. Turner, Attorney-in-Fact 05/06/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Includes 495,000 Restricted Stock Units (RSUs). The RSUs vest upon the satisfaction of both a service-based vesting condition and a liquidity event vesting condition. The liquidity event vesting condition will be satisfied upon the closing of the Issuer's initial public offering (IPO). The service-based vesting condition will be satisfied as to 25% of the RSUs on an annual basis beginning on the 12-month anniversary of January 5, 2026, subject to the reporting person's continued service through each vesting date. ( 2 )Each RSU represents a contingent right to receive one share of common stock of the Issuer. ( 3 )Each share of the Series A-1 Preferred Stock, Series A-2 Preferred Stock, Series A-3 Preferred Stock, Series C Preferred Stock, and Series D Preferred Stock is convertible into shares of the Issuer's common stock on a 1-for-1 basis, at the holder's election, and will automatically convert into shares of the Issuer's common stock upon the closing of the IPO pursuant to their terms. The Series A-1 Preferred Stock, Series A-2 Preferred Stock, Series A-3 Preferred Stock, Series C Preferred Stock, and Series D Preferred Stock have no expiration date. ( 4 )The shares are held by the Serafini Holding Trust Dated June 8, 2018, of which the reporting person is trustee and has voting and dispositive power. ( 5 )Fully vested. ( 6 )The shares subject to the option vest in equal monthly installments over 48 months measured from the one-month anniversary of October 6, 2023, subject to the reporting person's continuous service as of each such vesting date. ( 7 )Twenty-five percent of the shares subject to the stock option vested on each of February 1, 2025 and February 1, 2026. An additional twenty-five percent of the shares subject to the stock option will vest on February 1, 2027 subject to the Issuer's attainment of certain 2026 business objectives and the remaining twenty-five percent of the shares subject to the stock option will vest on February 1, 2028 subject to the Issuer's attainment of certain 2027 management and business objectives. An option tranche would be forfeited if the Issuer's board of directors determines that performance for the applicable year was below the threshold level and in each case is subject to the reporting person's continuous service through each such vesting date. ( 8 )The shares subject to the option vest in equal monthly installments over 48 months measured from the one-month anniversary of January 5, 2026, subject to the reporting person's continuous service as of each such vesting date.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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