A Single Man is a 2009 American period romantic drama film based on the 1964 novel of the same name by Christopher Isherwood. The directorial debut of fashion designer Tom Ford, the film stars Colin Firth, who was nominated for the Academy Award for Best Actor for his portrayal of George Falconer, a depressed gay British university professor living in Southern California in 1962.

Christopher William Bradshaw Isherwood was an Anglo-American novelist, playwright, screenwriter, autobiographer, and diarist. His best-known works include Goodbye to Berlin (1939), a semi-autobiographical novel which inspired the musical Cabaret (1966); A Single Man (1964), adapted as a film by Tom Ford in 2009; and Christopher and His Kind (1976), a memoir which "carried him into the heart of the Gay Liberation movement".