Cassius Clay rises from amateur boxer to 1960 Olympic gold medal winner. He turns professional and moves to Miami, sharpening his boxing skills and honing his genius for self-promotion. Meanwhile, he quietly joins the Nation of Islam and becomes a confidant of Malcolm X. In 1964, he shocks the world by upsetting the heavily favored Sonny Liston to win the heavyweight championship.

Cassius Clay joins the Nation of Islam and adopts the name Muhammad Ali. For three years, Ali dominates the heavyweight ranks but in 1967, he refuses induction into the U.S. Army and becomes one of the most reviled men in America. Ali is stripped of his title, convicted of draft evasion and forced into exile. In 1970, he triumphantly returns to the ring, but it's clear that he has lost a step.

Muhammad Ali faces Joe Frazier in the "Fight of the Century." Though he loses, Ali becomes a hero. The Supreme Court overturns Ali's conviction, validating his refusal to serve in the war in Vietnam and in 1974, Ali outduels Frazier, his greatest rival, in their highly anticipated rematch. But to complete his comeback, he must face the fearsome George Foreman.

Muhammad Ali shocks the world when he defeats George Foreman in Zaire, winning back the heavyweight title and becoming the most famous man on earth. He faces Joe Frazier in the brutal "Thrilla in Manila," and boxes for five more years. He is diagnosed with Parkinson's in 1984 but continues to travel the world spreading his Islamic faith, and becomes a symbol of peace and hope.