In 1920s Chicago, an Italian immigrant and notorious thug Antonio "Tony" Camonte works as a bodyguard for crime lord "Big" Louis Costillo. Siding with Costillo's disgruntled lieutenant John "Johnny" Lovo, Tony guns down his boss. Lovo takes over Costillo's territory in the South Side and has Tony and his associates, Angelo and Guino "Little Boy" Rinaldo, set up a lucrative bootlegging operation selling illegal beer to all of the bars there.
Tony urges Lovo to start moving in on the North Side, where the bootlegging is controlled by the Irish gangs of gangster O'Hara; Lovo refuses, ordering Tony to leave the North Side alone. Tony ignores these orders and starts attacking O'Hara's businesses while expanding his rackets to the North. Before long, Lovo is forced out of his position as Tony wins over their gang with his success.
Meanwhile, Tony pursues Johnny's girlfriend, Poppy. At first, she is dismissive of him but pays him more attention as his reputation rises, and he starts flaunting his wealth. She visits his "gaudy" apartment where he shows her his view of an electric billboard advertising Cook's Tours, which features the slogan which inspires him: "The World Is Yours".
Tony finally gets rid of O'Hara by having Guino assassinate him. O'Hara's successor, Tom Gaffney, declares war on the South Side and attempts to kill Tony in a restaurant with tommy guns—which an excited Tony quickly arms his own men with. The war results in Gaffney's gang being killed off one by one until he's forced to go into hiding. A group of prominent citizens, including the police chief, vow to bring Tony down for all the carnage and bloodshed he has inflicted on the city.
During a night out at the theatre, Tony learns that Gaffney and his entourage are at a nearby bowling alley. Leaving Angelo behind to watch the rest of the show, Tony personally kills Gaffney. Lovo's anger at Tony finally boils over when Tony openly flirts and dances with Poppy in front of him at dinner. Tony sees his beloved sister Francesca "Cesca" dancing with a stranger and takes her to his mother's home by force before hitting and yelling at her. A crew of gunmen later try to assassinate him, but he runs them off the road with his bulletproof car.
Suspecting Lovo's involvement, Tony goes to his office after bribing one of Lovo's men to call him and pretend to be part of the hit crew. When Lovo hangs up after claiming that he must have gotten the wrong number, Tony forces him to confess to the hit and then has Guino kill him. Tony, now the undisputed ruler of the city's underworld, takes Poppy on an expensive vacation to Florida to escape the police and media attention, while Cesca secretly visits Guino at Tony's office.
Paul Muni in the trailer for ScarfaceReturning home, Tony learns from his mother that Cesca has moved in with another man and rushes over to find her with Guino. He kills his friend in a jealous rage, and Cesca runs away in tears after revealing that they had just gotten married and were planning to surprise him. The police issue a warrant for Tony's arrest, and he barricades himself in his home while Angelo is killed trying to protect him.
Cesca slips inside, planning to kill her brother, but then gives in and admits her love for him. Tony and Cesca arm themselves, and Tony shoots at the police from the window with a Thompson submachine gun, laughing maniacally as he hits a number of policemen and sharpshooters across the street. Moments later, however, Cesca is killed by a stray bullet. Calling Cesca's name as the apartment fills with tear gas, Tony stumbles down the stairs just as the police break down his door. Tony pleads for his life but makes a break for it, resulting in the officers outside shooting him multiple times. He stumbles for a moment, falls in the gutter and dies. Above the sounds of cheering, the electric billboard blazes "The World Is Yours".
