Boxing legend Muhammad Ali died in hospital in the south-western US state of Arizona, his family said Friday.
Ali, 74, was being treated for respiratory complications near his home in Phoenix. He had suffered for more than 30 years from Parkinson's disease, which contributed to his physical deterioration.
The three-time heavyweight champion known as "The Greatest" - a nickname he bestowed upon himself - retired from boxing in 1981.
Ali was born Cassius Clay on January 17, 1942 in Louisville, Kentucky. He won the Olympic gold medal in the light-heavyweight division, and turned professional shortly afterward.
At the age of 22, he knocked out heavyweight champion Sonny Liston in a quick and stunning upset. He then joined the Nation of Islam and became Ali, publicly rejecting his "slave name."
He became a polarizing figure as a brash representative of the US civil rights movement, and as a potent symbol of resistance to the nation's war in Vietnam, when he refused to be conscripted into the military.
"I ain't got no quarrel with them Viet Cong," he declared. "No Viet Cong ever called me nigger."
He was convicted of draft evasion, and had his boxing title stripped from him, but appealed all the way to the Supreme Court, which overturned the conviction in 1971.
He would go on to regain and lose the title twice more.
Ali's most famous fights were the three epic battles he waged against Joe Frazier, and his upset defeat of George Foreman at the relatively advanced age of 32.
He used his international fame to spread the appeal of the sport, bringing the third Frazier bout to Manila, Philippines, and to stage the famous "Rumble in the Jungle" in Kinshasa, Zaire, now named Democratic Republic of Congo.
The BBC called Ali the Sports Personality of the Century, and he was one of the most-recognized people worldwide.