Serenity is a 2005 science-fiction film written and directed by Joss Whedon. It is set in the universe of the canceled Fox science fiction television series Firefly, taking place a few months after the events of the final episode. Like the television series that spawned it, Serenity is a science fiction Western, using elements of both genres. The film was released in the US on September 30, 2005.

Set 500 years in the future, Serenity is the story of the captain and crew of a transport and cargo ship. Their lives of petty crime are interrupted by a psychic passenger who carries a dangerous secret.

Joss Whedon, the Oscar- and Emmy-nominated writer/director responsible for the worldwide television phenomena of Buffy the Vampire Slayer and Angel, now applies his trademark compassion and wit to a small band of galactic outcasts 500 years in the future in his feature film directorial debut, Serenity.