Muhammad Ali born Cassius Marcellus Clay Jr. on 17 January 1942, was an American professional boxer, widely regarded as one of the most significant and celebrated sporting figures of the 20th century. From early in his career, Ali was known as an inspiring, controversial and polarizing figure both inside and outside the ring. Clay was born in Louisville, Kentucky, and began training when he was 12 years old. At 22, he won the world heavyweight championship from Sonny Liston in an upset in 1964. Ali remains the only three-time lineal world heavyweight champion; he won the title in 1964, 1974, and 1978. Between 25 February 1964, and 19 September 1964, Ali reigned as the heavyweight boxing champion. Nicknamed "The Greatest", he was involved in several historic boxing matches. Ali retired from boxing in 1981. At a time when most fighters let their managers do the talking, Ali, inspired by professional wrestler "Gorgeous George" Wagner, thrived in—and indeed craved—the spotlight, where he was often provocative and outlandish. Ali sadly passed away on 3 June 2016 at the age of 74.