The two fights between Muhammad Ali and Sonny Liston for boxing's World Heavyweight Championship were among the most controversial fights in the sport's history. Sports Illustrated magazine named their first meeting, the Liston–Clay fight, as the fourth greatest sports moment of the twentieth century.

Muhammad Ali was an American professional boxer and activist. Nicknamed "the Greatest", he is regarded as one of the most significant sports figures of the 20th century and is often regarded as the greatest heavyweight boxer of all time. He held the Ring magazine heavyweight title from 1964 to 1970. He was the undisputed champion from 1974 to 1978 and the WBA and Ring heavyweight champion from 1978 to 1979. In 1999, he was named Sportsman of the Century by Sports Illustrated and the Sports Personality of the Century by the BBC.