Muhammad Ali was a legendary boxer who is widely considered to be one of the greatest athletes of all time. He was born Cassius Marcellus Clay Jr. in 1942 and changed his name after converting to Islam in 1964. Ali was known for his incredible speed, agility, and strength in the ring, as well as his outspokenness and activism outside of it. He won 56 of his 61 professional fights, including 37 knockouts, and was the first fighter to win the world heavyweight championship three times.