Initial Statement of Beneficial Ownership (Form 3)

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF 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

OMB APPROVAL OMB Number: 3235-0104 Estimated average burden hours per response... 0.5

(Print or Type Responses)

1. Name and Address of Reporting Person * Brudnick Jonathan A. 2. Date of Event Requiring Statement (Month/Day/Year) 10/17/2025 3. Issuer Name and Ticker or Trading Symbol Six Flags Entertainment Corporation/NEW [FUN] (Last) (First) (Middle) 250 WEST 55TH STREET,, FLOOR 34 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) 5. If Amendment, Date Original Filed (Month/Day/Year) (Street) NEW YORK, NY 10019 6. Individual or Joint/Group Filing (Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5) Common Stock, par value $0.01 per share 5,030,000 I See footnotes(1)(2)(3)(4)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
	Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Cash Settled Swap	(5)(6)	06/03/2027	Common Stock	2,209,648	$28.6892	I	See footnotes(1)(2)(3)(4)
Cash Settled Swap	(5)(6)	06/03/2027	Common Stock	1,605,352	$28.6115	I	See footnotes(1)(2)(3)(4)
Cash Settled Swap	(5)(6)	06/03/2027	Common Stock	1,180,000	$29.0555	I	See footnotes(1)(2)(3)(4)

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Brudnick Jonathan A. 250 WEST 55TH STREET, FLOOR 34 NEW YORK, NY 10019	X
Ferguson Scott D. 250 WEST 55TH STREET, FLOOR 34 NEW YORK, NY 10019	X
Sachem Head Capital Management LP 250 WEST 55TH STREET, FLOOR 34 NEW YORK, NY 10019	X
Uncas GP LLC 250 WEST 55TH STREET, FLOOR 34 NEW YORK, NY 10019	X
Sachem Head GP LLC 250 WEST 55TH STREET, FLOOR 34 NEW YORK, NY 10019	X

Signatures

/s/ Michael D. Adamski, as Attorney-in-Fact		10/27/2025
**Signature of Reporting Person		Date
/s/ Michael D. Adamski, as Attorney-in-Fact		10/27/2025
**Signature of Reporting Person		Date
/s/ Michael D. Adamski, as General Counsel		10/27/2025
**Signature of Reporting Person		Date
/s/ Michael D. Adamski, as General Counsel		10/27/2025
**Signature of Reporting Person		Date
/s/ Michael D. Adamski, as General Counsel		10/27/2025
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(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)	In addition to Jonathan Brudnick, this Form 3 is being filed jointly by Sachem Head Capital Management LP ("Sachem Head"), Uncas GP LLC ("SH Management"), Sachem Head GP LLC ("Sachem Head GP"), and Scott D. Ferguson, a citizen of the United States (Mr. Ferguson and, together with Sachem Head, SH Management, Sachem GP, and Mr. Brudnick, the "Reporting Persons"). Each of the Reporting Persons has the same business address as Mr. Brudnick and may be deemed to be the beneficial owner of certain of the securities reported on this Form 3 (the "Subject Securities") for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended. Each of the Reporting Persons disclaims any beneficial ownership of any of the Subject Securities, except to the extent of any pecuniary interest therein.
(2)	Includes securities directly owned by Sachem Head LP ("SH"), Sachem Head Master LP ("SHM"), and SH Stony Creek Master Ltd. ("Stony Creek Master" and, together with SH and SHM, the "Sachem Head Funds"). Each of Sachem Head, as the investment adviser to the Sachem Head Funds, SH Management, as the sole general partner of Sachem Head, and Scott D. Ferguson, as the managing partner of Sachem Head may be deemed to beneficially own the securities directly owned by the Sachem Head Funds. As the general partner of SH and SHM, Sachem Head GP may be deemed to beneficially own the securities directly owned by SH and SHM.
(3)	The principal business of Sachem Head is to serve as investment advisor to certain affiliated funds, including the Sachem Head Funds. The principal business of SH Management is to serve as the sole general partner of Sachem Head. The principal business of Sachem Head GP is to serve as the general partner of certain affiliated funds, including SH and SHM. The principal occupation of Scott D. Ferguson is to serve as the managing partner of Sachem Head and the managing member of SH Management and Sachem Head GP.
(4)	Jonathan Brudnick is a partner at Sachem Head and also serves on the board of directors of Six Flags Entertainment Corporation (the "Issuer"). As a result, the Reporting Persons other than Mr. Brudnick may be deemed directors of the Issuer by deputization.
(5)	Under the cash-settled total return swaps referencing in the aggregate 4,995,000 shares of common stock (the "Cash Settled Swaps"), the respective Sachem Head Fund became a party to contracts with unaffiliated third party financial institutions pursuant to which a cash payment will be made by the counterparty to the respective Sachem Head Fund if the price of a share on the expiration date exceeds the reference price in column 4 and a cash payment will be made by the respective Sachem Head Fund to the counterparty if the price of a share on the expiration date is less than the reference price in column 4.
(6)	The Cash Settled Swaps do not give any Reporting Person direct or indirect voting, investment or dispositive control over any securities of the Issuer and do not require the counterparty thereto to acquire, hold, vote or dispose of any securities of the Issuer. Accordingly, the Reporting Persons disclaim any beneficial ownership of any Shares that may be referenced in the swap contracts or shares or other securities or financial instruments that may be held from time to time by any counterparty to the contracts.
Remarks: Exhibit 24.1 - Power of Attorney. Exhibit 24.2 - Power of Attorney.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, See Instruction 6 for procedure. Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.