FORM 4
[ ] 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 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 *

BAIN CAPITAL INVESTORS LLC	2. Issuer Name and Ticker or Trading Symbol

Trinseo S.A. [ TSE ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable)

_____ Director                      __ X __ 10% Owner
_____ Officer (give title below)      _____ Other (specify below)	
(Last)          (First)          (Middle)

200 CLARENDON STREET	3. Date of Earliest Transaction (MM/DD/YYYY)

8/12/2016		
(Street)

BOSTON, MA 02116
(City)        (State)        (Zip)	4. 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 Acquired, Disposed of, or Beneficially Owned	
1.Title of Security
(Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. 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				
ORDINARY SHARES  	8/12/2016  	 	S	  	8000000  	D	$49.15  	10669567  	I  	See Footnotes   (1) (2) (3)	

Table II - Derivative Securities Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities)	
1. Title of Derivate Security
(Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. 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	7. Title and Amount of Securities Underlying Derivative Security
(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					

Explanation of Responses:	
(  1) 	Represents ordinary shares of Trinseo S.A. held by Bain Capital Everest Manager Holding SCA ("BCEM Holding"), whose general partner is Bain Capital Everest Manager S.a r.l. ("BCEM"). On August 12, 2016, BCEM Holding sold 8,000,000 Ordinary Shares. Following such sale, BCEM Holding held 10,669,567 Ordinary Shares.	
(  2) 	All of the outstanding share capital of BCEM is held by Bain Capital Europe Fund III, L.P. ("Europe Fund III") and, in that capacity, Europe Fund III has the power to appoint the managers of BCEM. Bain Capital Investors, LLC ("BCI") is the general partner of Bain Capital Partners Europe III, L.P. ("Partners Europe III"), which is the general partner of Europe Fund III. BCI is also the general partner of Bain Capital Partners X, L.P. ("Partners X"), which is the general partner of Bain Capital Fund X, L.P. ("Fund X"). Boylston Coinvestors, LLC is the general partner of BCIP Associates IV, L.P. ("BCIP IV"), BCIP Associates IV-B, L.P. ("BCIP IV-B"), BCIP Trust Associates IV, L.P. ("BCIP Trust IV") and BCIP Trust Associates IV-B, L.P. ("BCIP Trust IV-B," and, together with BCEM Holdings, BCEM, Europe Fund III, Partners Europe III, Fund X, Partners X, BCIP IV, BCIP IV-B and BCIP Trust IV, the "Bain Capital Entities").	
(  3) 	The governance, investment strategy and decision-making process with respect to the investments held by all of the Bain Capital Entities is directed by BCI's Global Private Equity Board. As a result, BCI may be deemed to share voting and dispositive power with respect to the shares of Trinseo S.A. held by BCEM Holding. BCI disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.	

Remarks:
2 of 2	

Reporting Owners	
Reporting Owner Name / Address	Relationships	
	Director	10% Owner	Officer	Other	
BAIN CAPITAL INVESTORS LLC
200 CLARENDON STREET
BOSTON, MA 02116		X			
BCIP Trust Associates IV-B, L.P.
200 CLARENDON STREET
BOSTON, MA 02116		X			

Signatures		
BCIP TRUST ASSOCIATES IV-B, L.P. By: Boylston Coinvestors, LLC, its general partner By: /s/ Stephen Thomas, Name: Stephen Thomas, Title: Authorized Signatory		8/16/2016	
** Signature of Reporting Person		Date
	
BAIN CAPITAL INVESTORS, LLC, By: /s/ Stephen Thomas, Title: Managing Director		8/16/2016	
** Signature of Reporting Person		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).	
Note:	File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.	
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