SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP 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: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* BAIN CAPITAL INVESTORS LLC (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip)	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)
	3. Date of Earliest Transaction (Month/Day/Year) 03/24/2016
	4. If Amendment, Date of Original Filed (Month/Day/Year)	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. 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
ORDINARY SHARES	03/24/2016		S		10,600,000	D	$35.63	26,669,567	I	See Footnotes(1)(2)(3)

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 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: 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

1. Name and Address of Reporting Person* BAIN CAPITAL INVESTORS LLC (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Bain Capital Everest Manager Holding SCA (Last) (First) (Middle) 4 LOU HEMMER, L-1748 GRAND-DUCHY OF LUXEMBOURG (Street) N4 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Bain Capital Everest Manager S.a.r.l. (Last) (First) (Middle) 4 LOU HEMMER, L-1748 GRAND-DUCHY OF LUXEMBOURG (Street) N4 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Bain Capital Europe Fund III, L.P. (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Bain Capital Partners Europe III, L.P. (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Bain Capital Fund X LP (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Bain Capital Partners X, L.P. (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* BCIP Associates IV, L.P. (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* BCIP Associates IV-B, L.P. (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* BCIP Trust Associates IV, L.P. (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

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 March 24, 2016, BCEM Holding sold 10,600,000 Ordinary Shares. Following such sale, BCEM Holding held 26,669,567 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., which is the general partner of Europe Fund III. In addition to being the general partner of Bain Capital Partners Europe III, L.P., which is the general partner of Europe Fund III, BCI is the general partner of Bain Capital Partners X, L.P., which is the general partner of Bain Capital Fund X, L.P. Boylston Coinvestors, LLC is the general partner of BCIP Associates IV, L.P., BCIP Associates IV-B, L.P., BCIP Trust Associates IV, L.P. and BCIP Trust Associates IV-B, L.P.

3. The governance, investment strategy and decision-making process with respect to the investments held by all of the Bain Capital funds 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:

	BAIN CAPITAL EVEREST MANAGER HOLDING SCA, BY: Bain Capital Everest Manager S.a.r.l., its general partner, By: /s/ Stephen Thomas, Name: Stephen Thomas, Title: Manager	03/28/2016
	BAIN CAPITAL EVEREST MANAGER S.a.r.l., By: /s/ Stephen Thomas, Name: Stephen Thomas, Title: Manager	03/28/2016
	BAIN CAPITAL EUROPE FUND III, L.P., BY: Bain Capital Partners Europe III, L.P., its general partner, BY: Bain Capital Investors, LLC, its general partner, By: /s/ Stephen Thomas, Name: Stephen Thomas, Title: Managing Director	03/28/2016
	BAIN CAPITAL PARTNERS EUROPE III, L.P., BY: Bain Capital Investors, LLC, its general partner, By: /s/ Stephen Thomas, Name: Stephen Thomas, Title: Managing Director	03/28/2016
	BAIN CAPITAL FUND X, L.P., BY: Bain Capital Partners X, L.P., its general partner, BY: Bain Capital Investors, LLC, its general partner, By: /s/ Stephen Thomas, Name: Stephen Thomas, Title: Managing Director	03/28/2016
	BAIN CAPITAL PARTNERS X, L.P., BY: Bain Capital Investors, LLC, its general partner, By: /s/ Stephen Thomas, Name: Stephen Thomas, Title: Managing Director	03/28/2016
	BCIP ASSOCIATES IV, L.P., BY: Boylston Coinvestors, LLC, its general partner, By: /s/ Stephen Thomas, Name: Stephen Thomas, Title: Authorized Signatory	03/28/2016
	BCIP ASSOCIATES IV-B, L.P., BY: Boylston Coinvestors, LLC, its general partner, By: /s/ Stephen Thomas, Name: Stephen Thomas, Title: Authorized Signatory	03/28/2016
	BCIP TRUST ASSOCIATES IV, L.P., BY: Boylston Coinvestors, LLC, its general partner, By: /s/ Stephen Thomas, Name: Stephen Thomas, Title: Authorized Signatory	03/28/2016
	** Signature of Reporting Person	Date
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