Gosford Park is a 2001 satirical black comedy mystery film directed by Robert Altman and written by Julian Fellowes. It was influenced by Jean Renoir's French classic La Règle du jeu (The Rules of the Game).The film stars an ensemble cast, which includes Eileen Atkins, Bob Balaban, Alan Bates, Charles Dance, Stephen Fry, Michael Gambon, Richard E. Grant, Derek Jacobi, Kelly Macdonald, Helen Mirren, Jeremy Northam, Clive Owen, Ryan Phillippe, Maggie Smith, Kristin Scott Thomas, and Emily Watson. The story follows a party of wealthy Britons plus an American producer, and their servants, who gather for a shooting weekend at Gosford Park, an English country house. A murder occurs after a dinner party, and the film goes on to present the subsequent investigation from the servants' and guests' perspectives.

Development on Gosford Park began in 1999, when Bob Balaban asked Altman if they could develop a film together. Balaban suggested an Agatha Christie–style whodunit and introduced Altman to Julian Fellowes, with whom Balaban had been working on a different project. The film went into production in March 2001, and began filming at Shepperton Studios with a production budget of $19.8 million. Gosford Park premiered on 7 November 2001 at the London Film Festival. It received a limited release across cinemas in the United States in December 2001, before being widely released in January 2002 by USA Films. It was released in February 2002 in the United Kingdom.

The film was successful at the box office, grossing over $87 million in cinemas worldwide, making it Altman's second-most successful film after M*A*S*H. Widely acclaimed by critics, Gosford Park was nominated for seven Academy Awards, including Best Picture, Best Director and Best Supporting Actress for both Mirren and Smith, and won Best Original Screenplay; it was also nominated for nine British Academy Film Awards, winning two.

The TV series Downton Abbey—written and created by Fellowes—was originally planned as a spin-off of Gosford Park, but instead was developed as a standalone property inspired by the film, and set earlier in the 20th century (from 1912 to the mid-1920s).