When Cassius Clay wins a boxing gold medal at the 1960 Olympics, he returns home to Louisville, Kentucky, as a hero. Several prominent white residents form a consortium to sponsor his bid for a professional boxing career, but a racist incident at a country club reminds Cassius where he stands in local society, and he throws his gold medal into the Ohio River. Working with trainer Angelo Dundee and fight doctor Ferdie Pacheco, Cassius wins a series of bouts, drawing media attention with his ability to recite humorous poetry and “call the round” in which he knocks out his opponents. One evening, Cassius picks up an attractive blonde prostitute and drives her to an apartment building, but as she hurries to her door across the street, Cassius is waylaid by several black men from the nearby Muhammad’s Temple of Islam who convince him he would be better off meeting Malcolm X than cavorting with white women. Inside the storefront temple, Cassius is mesmerized by Malcolm X’s black nationalist message that the “white man” had taken away his name, his culture, his language, and, most important, his religion. Later, Drew “Bundini” Brown, formerly a promoter for Sugar Ray Robinson and other great black boxers, joins Cassius’s organization and counsels him that he must stop doing small-time fights and directly challenge heavyweight champion Sonny Liston. Cassius campaigns against Liston, insults him in the media, confronts him in a Las Vegas, Nevada, casino, and harasses him at his house until the champion agrees to fight. Cassius travels to Miami, Florida, to train for the match. Running in a park, he meets a pretty black woman named Ruby Sanderson and dates her. Malcolm X and several other Nation of Islam members arrive in town to join Cassius's entourage, which worries Angelo Dundee because the press has branded Malcolm X “the most dangerous man in America,” and any association with him could hurt Cassius’s boxing career. Bill McDonald, the promoter for the upcoming fight with Liston, threatens to call off the event if Cassius does not denounce the Nation of Islam, but when Cassius walks out and prepares to leave town, McDonald apologizes and asks only that Cassius wait until after the Liston fight to announce that he has joined the Nation of Islam. Following his upset knockout victory over Liston, Cassius reveals his religious conversion to the press and announces that Elijah Muhammad, the leader of the Nation of Islam, has personally given him a new name, Muhammad Ali, to replace his “slave name.” Furthermore, Herbert Muhammad, the son of Elijah Muhammad, is now his manager. At a celebratory party, Ali confronts Ruby, now his girl friend, and tells her he does not want her to wear makeup or revealing dresses around other men, and when he rips off her short skirt, she leaves him. During Herbert’s renegotiation of Ali’s financial arrangement with boxing promoters, one of the men hints that something bad might befall Ali, and Herbert replies that if anything happens to Ali or his friends, the Nation of Islam will shut down their fights. Later, at a Muslim bakery, Ali approaches Belinda Boyd, a modestly dressed young woman he saw earlier at a mosque, and asks her for a date. When the Selective Service reclassifies Ali as eligible for the military draft and inducts him into the Vietnam War, Ali creates a media storm by calling himself a conscientious objector and refusing to fight a white man’s war against another race. A federal judge sentences Ali to five years in prison and fines him $10,000 for draft evasion. When Ali’s lawyer appeals the case, the legal expenses cost Ali's life savings and he cannot replenish his funds because the boxing commission has taken away both his license and his World Heavyweight title. Despite Ali’s reduced circumstances, Belinda agrees to marry him, and he provides income by speaking to college students and others protesting the war. When the mayor of Atlanta, Georgia, invites Ali to fight there despite his unlicensed status, Ali’s promoters set up a match with a white boxer named Jerry Quarry. While Ali trains at a rural Georgia retreat, racists shoot at his cabin and threaten to kill him. He defeats Quarry, and when the U.S. Supreme Court overturns his conviction by recognizing his conscientious objector status, Ali regains his boxing license. Heavyweight champion Joe Frazier beats him at Madison Square Garden in New York, however, and Ali must work his way back to a rematch by taking what Angelo Dundee calls “junk fights.” After a series of victories, Ali’s jaw is broken by Ken Norton, and Belinda is hospitalized for shock. She tells Ali that she cannot watch him fight anymore because she “feels every blow” he takes. Rather than quit, Ali trains harder and wins a rematch with Norton, but the only way he can regain his World Heavyweight Championship title is to fight George Foreman. Overruling the warnings of his manager and trainer, Ali agrees to meet the stronger, more brutal Foreman in Zaire, Africa. In the early rounds, Ali takes a pounding, but he assures Angelo that he is letting the larger man “punch himself out,” and when the eighth round begins, Ali attacks the exhausted Foreman with a flurry of jabs, knocking him out and winning back the heavyweight crown he lost seven years earlier.