STX Entertainment is an American independent entertainment and media company. Founded in March 2014 by film producer Robert Simonds and TPG Growth managing partner Bill McGlashan, the studio produces film, television, and digital media projects.

In April 2020, STX announced that it would merge with the Indian studio Eros International. The merger was completed in July 2020, and STX became a division of ErosSTX. In December 2021, Jahm Najafi announced his intention to acquire STX from the merged company for $173 million–a sale completed in April 2022. Eros remains a minority, non-voting shareholder.

In 2012, Simonds and McGlashan began work on conceptualizing a media company based on the idea of producing medium-budget star-driven projects, a method that had gone out of style with Hollywood studios. The conversation led to the launch of STX Entertainment in 2014 (the "S" standing for Simonds, the company's founder; the "T" standing for TPG Growth, whose managing partner McGlashan helped launch the company; and the "X" standing for "secret project"), with the mission to finance, develop, produce, market, and distribute star-driven content around the world. Investors in the company included Hony Capital, Tencent, PCCW, TPG Growth, RTL Group and Liberty Global. Individual investors include Gigi Pritzker, Beau Wrigley, and Dominic Ng.

In September 2017, it was reported that STX was considering an initial public offering on the Hong Kong Stock Exchange (SEHK). It was reported that a listing on the SEHK could bring STX closer to Chinese investors and audiences. The Wall Street Journal stated that the company could be valued at $3.5 billion, after raising an additional $500 million following the IPO. In April 2018, the company filed for an IPO on the Hong Kong Stock Exchange.

STX called off its IPO in October 2018, citing the China–U.S. trade war, and conditions having deteriorated in Hong Kong due to turbulence in the mainland Chinese equity market. An overall co-funding agreement with Chinese company Huayi Brothers Media lapsed at the end of 2018, and in April 2019, co-founder Bill McGlashan was fired due to his being indicted in the college admissions bribery scandal.

In April 2020, STX announced that it would merge with the Indian film and television studio Eros International plc. Simonds stated that the merger would create "the first independent media company with the expertise and creative cultures of Hollywood and Bollywood, while also leveraging the important inroads both companies have made into the Chinese market." The combined company would be publicly traded, inheriting Eros' listing on the New York Stock Exchange. The merger was closed on July 30, 2020; the combined company unveiled a new logo and branding as ErosSTX in September. The combined entity raised $125 million of new equity funding and received $350 million in credit led by JPMorgan.

In December 2021, amid financial shortcomings following the merger, Jahm Najafi's Najafi Companies announced that it had reached an agreement to acquire STX Entertainment from ErosSTX for $173 million. However, in late January 2022, Lionsgate also emerged as a potential suitor, looking to absorb either part or whole of STX, but the deal was later rejected, leaving only Najafi as a potential suitor. In April 2022, Najafi Companies completed its acquisition of STX Entertainment. Eros Media World will retain a 15% non-voting stake in the company. In July 2022, shortly after STX's motion picture chairman Adam Fogelson departed for the studio, Deadline reported that STX was in talks with Lionsgate over a potential film distribution deal. Shortly after, it was reported that STX Entertainment's U.K. offices, including the London office housing STXinternational's headquarters, were gradually shutting down. Following the departure of STXinternational head John Friedberg to join Black Bear Pictures' international division, it was announced the latter company was nearing a deal with STX to handle part of its slate internationally. In November 2022, It was reported that STX's distribution and marketing operations would be shuttered and that Operation Fortune: Ruse de Guerre would go to a streaming service domestically, alternatives being considered for The Marsh King's Daughter, Lionsgate possibly taking over distribution for Ferrari and Greenland 2: Migration being packaged to other distributors. By February 2023, It was reported that Lionsgate had already taken domestic rights from Operation Fortune: Ruse de Guerre with plans to release it theatrically on March 3, 2023. In July 2023, Neon bought the distribution rights for Ferrari with Neon releasing it on December 25, 2023.

At launch, the film division of STX focused its efforts on creating a new model. Rather than pursuing the traditional distribution process, the company secured direct distribution agreements with North American theater chains AMC, Regal, Cinemark, Goodrich, Marcus Theatres, and Carmike Cinemas. In early 2015, the company signed a multiyear television output agreement to release films exclusively to Showtime Networks and its channels Showtime, The Movie Channel, and Flix during the premium television window. The deal covers STX Films theatrical releases through 2019. In April 2015, the company entered into a multiyear partnership with Universal Studios Home Entertainment for Universal to handle marketing, sales, and distribution services for Blu-ray, DVD, and VOD platforms for STX Films theatrical titles in North America. Film distribution was transferred to Studio Distribution Services, LLC., a joint venture between UPHE and Warner Bros. Home Entertainment. That same month, STX Films closed a three-year slate deal with Huayi Brothers, one of China's largest film studios, enabling the companies to co-produce and co-distribute 12 to 15 films annually. In January 2017, STX Films signed a marketing and distribution agreement with Luc Besson's EuropaCorp Films USA to release their upcoming slate of films in the US. In February 2018, STX Films announced it would distribute Netflix and Martin Scorsese's mob drama The Irishman in China along with Media Asia Entertainment Group.