UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 26, 2017

Trinseo S.A.

(Exact name of registrant as specified in its charter)

1000 Chesterbrook Boulevard, Suite 300,

Berwyn, Pennsylvania 19312

(Address of principal executive offices, including zip code)

(610) 240-3200

(Telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

o            Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o            Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o            Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o            Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company o

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Item 8.01                      Other Events.

Trinseo S.A. (the “Company”) will hold an Extraordinary General Meeting of Shareholders on November 28, 2017 (the “Extraordinary Meeting”) in the Grand Duchy of Luxembourg. Under the Company’s articles of association, each shareholder who plans to attend the Company’s Extraordinary Meeting is required to notify the Company on or before the record date of October 17, 2017.  Any such notices to attend the Extraordinary Meeting in person should be directed to:

Attn: Corporate Secretary — Notification to Attend Extraordinary General Meeting

Trinseo S.A.

1000 Chesterbrook Boulevard, Suite 300,

Berwyn, Pennsylvania 19312.

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SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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