Cat Ballou is a 1965 American western comedy film starring Jane Fonda and Lee Marvin, who won an Academy Award for Best Actor for his dual role. The story involves a woman who hires a notorious gunman to protect her father's ranch, and later to avenge his murder, only to find that the gunman is not what she expected. The supporting cast features Tom Nardini, Michael Callan, Dwayne Hickman, and Nat King Cole and Stubby Kaye, who together perform the film's theme song, and who appear throughout the film in the form of travelling minstrels or troubadours as a kind of musical Greek chorus and framing device.

The film was directed by Elliot Silverstein from a screenplay by Walter Newman and Frank Pierson adapted from the 1956 novel The Ballad of Cat Ballou by Roy Chanslor, who also wrote the novel filmed as Johnny Guitar. Chanslor's novel was a serious Western, and though it was turned into a comedy for the film, the filmmakers retained some darker elements. The film references many classic Western films, notably Shane. The film was selected by the American Film Institute as the 10th greatest Western of all time in its AFI's 10 Top 10 list in 2008.