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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(Print or Type Responses)

1. Name and Address of Reporting Person * Fernandez Gomez Luciano 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 __X__ Officer (give title below) _____ Other (specify below) Co-Chief Executive Officer (Last) (First) (Middle) C/O KLAVIYO, INC. 125 SUMMER STREET, 6TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 08/15/2026 (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 08/15/2026 C(1) 7,001 A (2) 2,330,706 D Series A Common Stock 08/15/2026 F(3) 29,133 D $18.49 2,301,573(4) 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)

08/15/2026

C(1)

7,001

(2)

(2)

Series A Common Stock

7,001

$18.49

48,999(5)

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Fernandez Gomez Luciano C/O KLAVIYO, INC. 125 SUMMER STREET 6TH FLOOR BOSTON, MA 02110	X		Co-Chief Executive Officer

Signatures

/s/ Landon Edmond, Attorney-in-Fact		08/18/2026
**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 7,001 shares of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), automatically converted into shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), in connection with tax withholding obligations related to the vesting and settlement of restricted stock units ("RSUs").
(2)	Each share of 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 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)	Represents shares of Series A Common Stock withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of RSUs.
(4)	Consists of (i) 287,984 shares of Series A Common Stock; (ii) 820,351 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan (the "Plan"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 1,193,238 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.
(5)	Consists of 48,999 shares of Series B Common Stock.

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