Trinseo is a global materials company, focusing particularly on the manufacture of plastics, latex, and synthetic rubber. Among the materials it makes is the plastic for Lego. Trinseo (formerly known as Styron) was part of the Dow Chemical Company until Dow grouped several of its businesses for potential sale in 2009. In 2010, under the name Styron, those holdings were sold to private equity firm Bain Capital for $1.63 billion. As of 2016, Bain sold all of its stock in Trinseo, grossing $1.69 billion for 37,269,567 shares, resulting in Trinseo's “full independence as a public company.”

The company offers a broad line of plastics, latex and synthetic rubber, which are used primarily in the automotive, appliances, electronics, packaging, paper & board, carpet, and tire industries, among others. Trinseo materials are used widely, in cars and trucks, home appliances, consumer goods, electronics, electrical & lighting, building & construction, medical supplies, and packaging.

As of June 12, 2014, Trinseo is listed on the New York Stock Exchange as NYSE: TSE. Christopher D. Pappas is the current President and CEO.

Trinseo's precursor Styron was formed in August 2009 when Dow Chemical Company combined several of its businesses--styrenics; polycarbonate and compounds & blends; Dow Automotive plastics; emulsion polymers (paper and carpet latex); and synthetic rubber — as part of a larger process of identifying and selling non-strategic assets. Several private equity firms bid on Styron, including TPG Capital, Apollo Management, and Lotte Group. On March 2, 2010, Bain Capital announced that it would purchase the newly formed company for $1.63 billion, with Dow retaining a 7.5% stake. The sale was finalized in June 2010.

The name Trinseo was chosen in 2012. By February 2015, all legal entities worldwide had changed to the name Trinseo.

As of 2016, Bain sold all of its stock in Trinseo, grossing $1.69 billion for 37,269,567 shares, resulting in Trinseo's “full independence as a public company.”

Trinseo is headquartered in Berwyn, Pennsylvania. Trinseo comprises approximately 2,100 employees in 30 countries.

Styron was the #67 ranked chemical company globally in 2011, posting sales of $6.193B. As of 2013, Trinseo's annual revenue was approximately $5.54 billion. As of 2017 the company reported a net income of $310 million and an adjusted EBITDA guidance of $580 million.

Trinseo owns a 50% stake in North American polystyrene producer American Styrenics LLC, a joint venture based in the Woodlands, Texas. Trinseo previously held a 50% stake in Sumika Styron Polycarbonate Limited, but sold this to Sumitomo Chemical in 2017. In 2016 Trinseo signed an agreement to sell its Brazil-based businesses to Qoppar Participacoes Ltda.

As of 2017, Trinseo announced its first acquisition, the Italian plastics firm Applicazioni Plastiche Industriali. API's softer plastics will complement Trinseo's harder plastics. On September 27, 2017, Trinseo opened a new research and development center in Terneuzen, Netherlands.

Trinseo's IPO debuted on June 12, 2014, listed as NYSE: TSE. All shares were sold in the offering, and raised over $190 million.