Brokeback Mountain is a 2005 neo-Western romantic drama film directed by Ang Lee and produced by Diana Ossana and James Schamus. Adapted from the 1997 short story by Annie Proulx, the screenplay was written by Ossana and Larry McMurtry. The film stars Heath Ledger, Jake Gyllenhaal, Anne Hathaway, and Michelle Williams. Its plot depicts the complex romantic relationship between two American cowboys, Ennis Del Mar and Jack Twist, in the American West from 1963 to 1983.

Lee became attached to the project in 2001 after previous attempts to adapt Proulx's story into a film did not materialize. Focus Features and River Road Entertainment would jointly produce and distribute the film. After Ledger and Gyllenhaal's casting was announced in 2003, filming commenced in various locations in Alberta in 2004. Brokeback Mountain premiered at the 2005 Venice International Film Festival, where it won the Golden Lion, and was released to theaters on December 9 that year.

The film received widespread critical acclaim, with high praise for the performances of Ledger and Gyllenhaal. It emerged as a commercial success at the box-office, grossing over $178 million worldwide against its $14 million budget, and won various accolades. At the 78th Academy Awards, Brokeback Mountain was nominated for Best Picture and won for Best Director, Best Adapted Screenplay, and Original Score. It garnered seven nominations at the 63rd Golden Globe Awards, winning Best Motion Picture — Drama, Best Director and Best Screenplay and Best Song. At the 59th British Academy Film Awards, Brokeback Mountain had nine nominations, winning Best Film, Best Direction, Best Adapted Screenplay and Best Supporting Actor (Gyllenhaal).

Brokeback Mountain was subject to controversies; its loss to Crash (2004) for the Academy Award for Best Picture, subsequent censorship, and criticism from conservative media outlets received significant attention. The sexuality of the main characters has been subject to discussion. Brokeback Mountain has also been regarded as a turning point for the advancement of queer cinema into the mainstream. In 2018, the film was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant".