Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

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

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1. Name and Address of Reporting Person * Oulman Roxanne 2. Issuer Name and Ticker or Trading Symbol Klaviyo, Inc. [KVYO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O KLAVIYO, INC., 125 SUMMER STREET, 6TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 06/09/2026 (Street) BOSTON, MA 02110 4. If Amendment, Date Original Filed (Month/Day/Year) 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 (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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 Series A Common Stock 06/09/2026 A 14,822(1) A $ 0 29,174 D Series A Common Stock 06/11/2026 C 8,169 A (2) 37,343(3) D

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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 (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

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 (Month/Day/Year)

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 B Common Stock

(2)

06/11/2026

C

8,169

(2)

(2)

Series A Common Stock

8,169

$ 0

15,165

D

Series B Common Stock

(2)

(2)

(2)

Series A Common Stock

46,666

46,666(4)

I

By Roxanne Oulman 2025 GRAT(5)

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Oulman Roxanne C/O KLAVIYO, INC. 125 SUMMER STREET, 6TH FLOOR BOSTON, MA 02110	X

Signatures

/s/ Landon Edmond, Attorney-in-Fact		06/11/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	Represents restricted stock units ("RSUs") awarded under the Issuer's 2023 Stock Option and Incentive Plan (the "Plan"), each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), upon vesting and settlement. The RSUs vest in full upon the earlier of (i) June 9, 2027 or (ii) the date of the Issuer's next annual meeting of stockholders, in each case subject to the Reporting Person's continued service as a member of the Issuer's board of directors through such vesting date.
(2)	Each share of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.
(3)	Consists of (i) 22,521 shares of Series A Common Stock and (ii) 14,822 unvested RSUs awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.
(4)	Reflects 46,666 shares of Series B Common Stock previously transferred from the Reporting Person to Roxanne Oulman 2025 GRAT.
(5)	Shares held by Roxanne Oulman 2025 GRAT, of which the Reporting Person serves as trustee. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose.

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