Muhammad Ali (born Cassius Marcellus Clay, Jr.; January 17, 1942) is an American former professional boxer, philanthropist and social activist. Considered a cultural icon, Ali was both idolized and vilified.

Originally known as Cassius Clay, Ali changed his name after joining the Nation of Islam in 1964, subsequently converting to Sunni Islam in 1975, and more recently practicing Sufism. In 1967, three years after Ali had won the World Heavyweight Championship, he was publicly vilified for his refusal to be conscripted into the U.S. military, based on his religious beliefs and opposition to the Vietnam War. Ali stated, "I ain't got no quarrel with them Viet Cong... No Viet Cong ever called me nigger" – one of the more telling remarks of the era.

Widespread protests against the Vietnam War had not yet begun, but with that one phrase, Ali articulated the reason to oppose the war for a generation of young Americans, and his words served as a touchstone for the racial and antiwar upheavals that would rock the 1960s. Ali's example inspired Martin Luther King Jr. – who had been reluctant to alienate the Johnson Administration and its support of the civil rights agenda – to voice his own opposition to the war for the first time.