Muhammad Ali was defeated by five different boxers during his professional boxing career:

• Joe Frazier : Ali's first loss came in 1971 in the "Fight of the Century," where Frazier won by unanimous decision after 15 rounds, defending his heavyweight title

• Ken Norton : In 1973, Norton defeated Ali by split decision and notably broke Ali's jaw during the fight

• Leon Spinks : Spinks beat Ali in 1978 via split decision in a 15-round bout, marking Ali's third loss

• Larry Holmes : Holmes dominated Ali in 1980, leading to Ali's trainer stopping the fight in the 11th round. This fight showed Ali's decline due to age and health issues

• Trevor Berbick : Berbick was the last to defeat Ali in 1981 by unanimous decision in Ali's final professional fight

Ali's overall professional record was 56 wins and 5 losses, with 37 wins by knockout