Catherine Cat Ballou (Fonda), an aspiring schoolteacher, is traveling home by train to Wolf City, Wyoming, to see her rancher father, Frankie Ballou (John Marley). While en route she unwittingly helps accused cattle rustler Clay Boone (Michael Callan) escape the sheriff (Bruce Cabot), when Boone's Uncle Jed (Dwayne Hickman), a drunkard disguised as a preacher, distracts the lawman. She reaches the ranch to find that the Wolf City Development Corporation is trying to take the ranch away from her father, whose only defender is an educated young Indian boy, Jackson Two-Bears (Tom Nardini). Clay and Jed appear and are talked into reluctantly helping Catherine. She also sends a letter and $50 to legendary gunfighter Kid Shelleen (Lee Marvin) to hire him to come and help protect her father from fast-drawing Tim Strawn (also Marvin), alias Silvernose, the hired killer who is threatening Frankie.
Shelleen arrives, a drunken stumble-bum who is literally unable to hit the broad side of a barn when he shoots and whose pants fall down when he draws his gun. Strawn kills Frankie, and when the townspeople refuse to bring him to justice, Catherine becomes the outlaw Cat Ballou and vows to take revenge on the town and on Wolf City Development. She and her four gang members rob a train carrying the Wolf City payroll, and Shelleen, inspired by his love for Cat (unrequited because she loves Clay), drys out, shapes up and again looking and acting like the legendary gunfighter he was, finds and kills Strawn (off-screen) in a gunfight. Later he casually reveals that Strawn was his brother.
Cat, posing as a Soiled Dove, confronts town boss and head of Wolf City Development, Sir Harry Percival (Reginald Denny). A struggle ensues, Sir Harry is killed, and Cat is sentenced to be hanged on the gallows. Shelleen falls off the wagon and as Cat is led up the gallows stairs he sits on his horse (who looks as drunk as his rider!) as both lean against a building.
Just after the noose is placed around her neck, Uncle Jed (again as a fake preacher) cuts the rope as she falls through the trapdoor. Shelleen drunkenly shoots up the town as her gang then spirits her away in a daring rescue. Close credits with the gang happily riding away as drunken Kid Shelleen tries desperately to stay on his horse.
Also features Stubby Kaye and, in his last on-screen movie appearance, Nat King Cole, as a pair of traveling, banjo-playing minstrels.
This film provides examples of:
- The Alleged Steed: Kid Shelleen's horse, who is apparently as drunk as he is.
- Black and Gray Morality: The only reason Cat became an outlaw was due to the townspeople's indifference to her father's murder. As such, since she can't get justice within the law, she goes for vengeance outside of it.
- Book Safe: Uncle Jed, disguised as a preacher, produces a knife from his Bible and uses it to cut the rope on the gallows as it is placed around Cat's neck.
- Earlier in the film, he uses the same Bible to hide a gun.
- Cain and Abel: Shelleen and Strawn are brothers.
- Character Title
- Comically Missing the Point: Shelleen completely misunderstands why the room is full of candles... at a funeral. He even starts singing Happy Birthday to You!.
- Drunken Master: When Kid Shelleen is sober he shakes too much with the DTs to hit anything, and when he's drunk he staggers and stumbles so much he can hardly hold a gun. But for a short time — after he's had a few drinks, but before he gets drunk — he is again the deadly-accurate, fast-shooting gunfighter he used to be. Unfortunately this time only lasts for a few minutes.
- End of an Era: Par for a Western tale, the approach and rise of urban developments puts an end to ranching and homesteading and any danger to the Wild West. Shelleen jokes about an ice skating rink at the OK Corral, in a bittersweet tone.
- Eye Patch Of Power: Parodied by Strawn's tin nose. Also used for a "I'd be more afraid of the guy who gave him that scar" Shout-Out to Seven Samurai and The Magnificent Seven Samurai.
- Greek Chorus: Professor Sam the Shade (Stubby Kaye) and the Sunrise Kid (Nat King Cole).
- Handsome Lech: Clay. Oh so very much.
- Hero with Bad Publicity: By the end of the movie, everyone in Wolf City hates Cat for costing them the railroad.
- Improbable Aiming Skills: Inverted, Kid Shelleen literally misses the broad side of the barn.
- In Medias Res: The movie starts with Stubby Kaye and Nat King Cole singing about Cat's impending execution.
- In Vino Veritas
- Justified Criminal: Due to the reasons listed in the trope above
- Logo Joke: The Columbia Pictures Torch Lady becomes animated and wears Cat Ballou's gunslinger clothes, then takes out her guns and fires them, seen here.
- The Noseless: Tim Strawn is known as Silvernose due to his prosthetic replacement.
- The Oner: The square dance was originally intended to be this, and was shot in one take but cuts were added afterwards.
- Outlaw Town: Hole in the Wall.
- Railroad Baron: Sir Harry Percival owner of the Wolf City Development Corporation. So much so that he is allowed to have Cat's father murdered without the town batting an eye.
- Reality Ensues: Nobody in Wolf City likes Cat for killing the man who built up Wolf City, no matter how despotic he was.
- Schoolmarm: Cat, before she turns into an outlaw.
- Sibling Rivalry: Between Strawn and Shelleen.
- These Hands Have Killed: Cat has this reaction when she kills Sir Harry.
- Train Job: Cat and her gang rob the train carrying the Wolf City payroll.
- Warts and All: Catherine is dismayed to find that Shelleen, whom she hired due to his high reputation with a gun, is constantly drunk and uncoordinated as a result. Even his horse shows a similar laid back attitude.