Muhammad Ali was a legendary boxer and social activist who is widely regarded as one of the greatest athletes of all time. He was born Cassius Marcellus Clay Jr. in 1942 in Louisville, Kentucky, and changed his name to Muhammad Ali after converting to Islam in 1964. He won 56 of his 61 professional fights, including 37 knockouts, and was the first fighter to win the world heavyweight championship three times. Ali was also an outspoken advocate for civil rights and social justice, and was awarded the Presidential Medal of Freedom in 2005.