Plot

In Chicago, circa 1924, naive Roxie Hart (Renée Zellweger) visits a nightclub The Onyx, where star Velma Kelly (Catherine Zeta-Jones) performs ("All That Jazz"). Unknown to anyone, Velma had brought a gun to the club. Velma performs on stage was supposed to be a double act with her sister, but that night she performs alone. Seeking stardom, Roxie begins an affair with furniture salesman Fred Casely (Dominic West), who claims to know the manager and Roxie hopes will get her a vaudeville gig. Fred takes Roxie away from the club saying that the meeting with the manager is taken care of. They go to Roxie's apartment where Fred ravishes Roxie in her bed.

After the show, Velma is arrested for killing her husband and sister, Veronica, after finding them in bed together. Later, after they have had sex, Fred tells Roxie that she will never have her own act as she is a 2-bit talent with skinny legs. Fred reveals to Roxie that he lied about his connections in order to sleep with her and throws her around when she tries to get clingy. At this point Roxie, in a fit of rage, shoots Fred three times, killing him.

Roxie convinces her husband, Amos (John C. Reilly), to take the blame, telling him it was a burglar and that he needn't worry, he'll get off. However, when evidence of Roxie's infidelity is uncovered, Amos recants and tells the police that Casely was dead when he arrived home ("Funny Honey"). Roxie is arrested, with District Attorney Martin Harrison declaring she faces execution by hanging.

Upon her arrival, she is sent to Murderess' Row-under the care of the corrupt but nurturing Matron "Mama" Morton (Queen Latifah), who takes bribes and supplies her prisoners with cigarettes and contraband ("When You're Good to Mama")-to await trial.

Roxie meets Velma and learns the backstories of the other women in Murderess' Row ("Cell Block Tango"). Roxie decides that she wants to engage Velma's lawyer, Billy Flynn (Richard Gere) ("All I Care About"), and convinces her husband to talk to him. Flynn is a duplicitous, greedy, smooth-talking lawyer who turns his clients into celebrities to gain public support for them.

Flynn and Roxie manipulate the press at a press conference, reinventing Roxie as an originally virtuous Southern woman corrupted by the city's decadent nightlife; she claims that she had the affair with Casely because Amos was always working, but repented and left Casely for Amos, and Casely jealously attacked her ("We Both Reached for the Gun"). The press believes the story; praised by the public as a tragic heroine, Roxie becomes an overnight sensation ("Roxie").

Roxie becomes the new infamous celebrity of the Cook County Jail ("Roxie"), much to Velma's disgust and Mama's delight. Velma, desperate to get back into the limelight, tries to talk Roxie into opening a vaudeville act with her once they get out of jail ("I Can't Do It Alone"). Seeking revenge for an earlier mocking, Roxie haughtily refuses, and Roxie and Velma become locked in a rivalry to outshine each other.

After an heiress Kitty Baxter (Lucy Liu) is arrested for a triple homicide (she killed her husband and the two women in bed with him), Roxie finds herself ignored by the paparazzi and neglected by Flynn. After being told by Velma that her name isn't in the paper, Roxie manages to steal back the limelight by claiming to be pregnant, which is confirmed by a doctor, whom it is implied she seduced.

Amos is ignored by the press ("Mister Cellophane"), and Flynn, to generate more sympathy for Roxie, convinces him that the child is Casely's, and that he should divorce Roxie in the midst of her predicament. Roxie decides to fire Flynn, believing she can now win on her own. However, when Katalin Helinszki, a Hungarian woman on Murderess' Row (the only inmate who insists on her own innocence), becomes the first woman in Cook County history to be executed by hanging, Roxie realizes the gravity of the situation and rehires Flynn. Roxie and Billy design their scheme to prove her innocence, by using her star power and sympathy vote.

Roxie's trial begins, and Flynn turns it into a media spectacle ("Razzle Dazzle") with the help of sensationalist newspaper reporters and radio personality Mary Sunshine (Christine Baranski). Flynn discredits witnesses, manipulates evidence and even stages a public reconciliation between Amos and Roxie when she claims the child is his. The trial seems to be going well for Roxie until Mama and Velma are listening to the trial and find Roxie's diary, and bring it to court.

In exchange for amnesty, Velma reads incriminating entries from the diary that could convict Roxie. Flynn discredits the diary, implying from its legalistic language that it was written by Harrison, who planted it as evidence ("A Tap Dance"). Roxie is acquitted, but her fame is eclipsed moments later when another woman, who had also shot her own husband, shoots her lawyer outside the courthouse. Flynn admits to Roxie that he tampered with her diary himself, in order to incriminate the DA and also free two clients simultaneously.

Roxie leaves the courthouse after Billy tells her that it is Chicago and she can't beat fresh blood off the walls. Amos remains loyal and excited to be a father, but Roxie cruelly reveals that she faked her pregnancy. It is implied, but never stated, that Amos leaves her at this point.

With nothing left, Roxie once more sets off to find a stage career, with little success ("Nowadays"). However, she is soon approached by Velma, also down on her luck, who is willing to revive a two-person act with Roxie. Roxie refuses at first, still not over the hate they shared for each other while in prison, but relents when Velma points out that "there's only one business in the world where that's not a problem at all: show business." The two murderesses, no longer facing jail time, finally become the enormous successes they have been longing to be ("Nowadays/Hot Honey Rag"). The film concludes with Roxie and Velma receiving a standing ovation from an enthusiastic audience that includes Mama and Billy.