Muhammad Ali claimed the World Boxing Association's heavyweight title three times. Ali reigned as world champion from 1964 to 1967, 1974 to 1978, and 1978 to 1979.
Following a successful amateur career, Ali burst onto the boxing scene with a gold medal at the 1960 Summer Olympics in Rome, when he was still known as Cassius Clay prior to his conversion to Islam.
The fighter was stripped of his first heavyweight title in 1967 and banned from the sport for over three years after refusing to serve in the military after he was drafted.
On Dec. 11, 1981, Ali entered the ring for the last time, losing to Trevor Berbick by unanimous decision in Nassau, Bahamas. Ali finished his career with 56 wins, including 37 by knockout, against just five defeats.