Stanley Ipkiss (JIM CARREY) is a mild-mannered bank employee who loves cartoons and wants to be like the wolf in old Tex Avery shorts, but doesn't have the personality for it. He's a simple nice guy who is disappointed that women don't seem to go for his type.
After being booted from the Coco Bongo, Edge City's most happening nightclub, Stanley's rental car breaks down on a bridge. Looking out at the water, he sees a mask floating, although he believes it's someone drowning. He goes right in, finds the mask, and eventually decides to try it on. When he does, he becomes a completely new man, one with more confidence, more vitality, and a lot more zaniness, just like the cartoons he watches.
At the same time, through robbing a bank, he crosses paths with Dorian Tyrell (PETER GREENE), an ambitious criminal who wants to lord over Edge City and had dispatched his men to rob that same bank in order to make it happen. With him, though not happily, is Tina Carlyle (CAMERON DIAZ), whom Stanley first meets at his bank when she supposedly wants to open an account, and is the main entertainment for Tyrell's Coco Bongo Club. Tyrell's actions and Stanley, when he's the mask, eventually come to a head.