Running out of space and time in a modernizing West, a band of outlaws led by Pike Bishop (William Holden) rides into the Texas border town of San Rafael to stick up the railroad office. The railroad, however, has hired a passel of bounty hunters to annihilate the Bunch. Led by Pike's old friend Deke Thornton, the vulturelike bounty hunters ambush the Bunch from the rooftops of the town, killing outlaws and townspeople with indiscriminate glee. Pike escapes, along with Dutch (Ernest Borgnine), Lyle and Tector Gorch (Warren Oates, Ben Johnson), and Angel (Jamie Sanchez). They are joined outside town by old Freddie Sykes (Edmond O'Brien), whereupon they discover that the bags of cash they took from the depot are dummies stuffed with worthless washer rings. Broke, they cross into Mexico, pursued by Thornton and his gang. The Bunch go to work for General Mapache (Emilio Fernandez), a cruel despot fighting on behalf of a corrupt government and against a popular revolution. After the Bunch steals guns for the general, Mapache seizes and tortures Angel. To avenge Angel, the Bunch confronts and kills Mapache, precipitating a sustained slaughter during which the members of the Bunch wipe out most of Mapache's army and are themselves killed. The survivors, Freddie Sykes and Deke Thornton, join forces with the peasant revolutionaries.

Sam Peckinpah modestly said that with The Wild Bunch he wasn't trying to make an epic but only to tell a simple story about bad men in changing times.