From Wikipedia, the free encyclopedia Muhammad Ali (born Cassius Marcellus Clay, Jr.; January 17, 1942) is an American former professional boxer,[1]philanthropist[2] and social activist.[2] Considered a cultural icon, Ali was perhaps one of the most idolized, vilified and complex public figures of the 20th century.[3][4] Originally known as Cassius Clay, Ali changed his name, after joining the Nation of Islam in 1964, the same year his friend Malcolm X would leave, subsequently converting to traditional Islam; Ali would follow suit in the '70s.