John T. Chance (John Wayne) is the main peacekeeper of the small Texas town Rio Bravo. He arrests Joe Burdette (Claude Akins) after the no-good murderer kills a man in cold blood during a bar fight. This doesn't sit well with Joe's brother Nathan (John Russell), and he causes tension in the town that puts Chance on guard.
Although outnumbered, Chance doesn't try and enlist the help of the hapless townsfolk to face up to the gang. He and his deputies -- disgraced drunk "Dude" (Dean Martin), the ornery, crippled Stumpy (Walter Brennan) and the hotshot new kid Colorado (Ricky Nelson) -- must find a way to hold out against the rancher's hired guns until the federal marshal arrives.