Muhammad Ali (/ɑːˈliː/;[4] born Cassius Marcellus Clay Jr.;[5] January 17, 1942 – June 3, 2016) was an American professional boxer and activist. Nicknamed "The Greatest", he is regarded as one of the most significant sports figures of the 20th century and is often regarded as the greatest heavyweight boxer of all time.[6][7][8] In 1999, he was named Sportsman of the Century by Sports Illustrated and the Sports Personality of the Century by the BBC.