FORM 3
        
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
                       
1. Name and Address of Reporting Person * ADVENT INTERNATIONAL CORP/MA 2. Date of Event Requiring Statement (MM/DD/YYYY)
6/16/2021 

 3. Issuer Name and Ticker or Trading Symbol ATI Physical Therapy, Inc. [ATIP]
(Last)       (First)       (Middle)
PRUDENTIAL TOWER, 800 BOYLSTON STREET,, SUITE 3300		 4. Relationship of Reporting Person(s) to Issuer (Check all applicable)_____ Director                          ___X___ 10% Owner
_____ Officer (give title below)        _____ Other (specify below)
(Street)
BOSTON, MA 02199      
(City)             (State)             (Zip)
 5. If Amendment, Date Original Filed(MM/DD/YYYY)
 

 6. Individual or Joint/Group Filing(Check Applicable Line)___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person

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)
Class A Common Stock, par value $0.0001 per share  130300000 (1) I  See Footnotes (2)(4)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(MM/DD/YYYY)		 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
Earnout Shares   (3)  (3) Class A Common Stock, par value $0.0001 per share  15000000   (3) I  See notes (2)(4)

Explanation of Responses:
(1)  See Exhibit 99.1 for text of footnote (1)
(2)  See Exhibit 99.1 for text of footnote (2)
(3)  See Exhibit 99.1 for text of footnote (3)
(4)  See Exhibit 99.1 for text of footnote (4)

Remarks:
Exhibit 99.1 (Signatures and Joint Filer Information) and Exhibit 99.2 (Joint Filer Information) are incorporated herein by reference. This Form 3 is the third of three Forms 3 being filed relating to the same event. The Form 3 has been split into three filings because there are more than 10 Reporting Persons in total, and the SEC's EDGAR filing system limits a single Form 3 to a maximum of 10 Reporting Persons. Each Form 3 will be filed by Designated Filer Advent International Corporation.

Form 3 of 3

Reporting Owners
Reporting Owner Name / Address
Relationships
Director 10% Owner Officer Other
ADVENT INTERNATIONAL CORP/MA
PRUDENTIAL TOWER, 800 BOYLSTON STREET,
SUITE 3300
BOSTON, MA 02199
X

Advent Partners GPE VII-B Cayman Limited Partnership
C/O ADVENT INTERNATIONAL CORPORATION
800 BOYLSTON STREET, SUITE 3300
BOSTON, MA 02199
X

Advent Partners GPE VII Limited Partnership
C/O ADVENT INTERNATIONAL CORPORATION
800 BOYLSTON STREET, SUITE 3300
BOSTON, MA 02199
X

Advent Partners GPE VII-A Cayman Limited Partnership
C/O ADVENT INTERNATIONAL CORPORATION
800 BOYLSTON STREET, SUITE 3300
BOSTON, MA 02199
X

Advent Partners GPE VII-A Limited Partnership
C/O ADVENT INTERNATIONAL CORPORATION
800 BOYLSTON STREET, SUITE 3300
BOSTON, MA 02199
X

GPE VII ATI Co-Investment Limited Partnership
C/O ADVENT INTERNATIONAL CORPORATION
800 BOYLSTON STREET, SUITE 3300
BOSTON, MA 02199
X

Advent International GPE VII, LLC
C/O ADVENT INTERNATIONAL CORPORATION
800 BOYLSTON STREET, SUITE 3300
BOSTON, MA 02199
X

Maldonado John L.
C/O ADVENT INTERNATIONAL CORPORATION
800 BOYLSTON STREET, SUITE 3300
BOSTON, MA 02199		 X


Petrone Carmine
C/O ADVENT INTERNATIONAL CORPORATION
800 BOYLSTON STREET, SUITE 3300
BOSTON, MA 02199		 X



Signatures
Advent International Corporation, /s/ James Westra, Name: James Westra, Title: General Counsel and Managing Partner 6/28/2021
**Signature of Reporting Person Date
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