Boxing icon Muhammad Ali has died aged 74, a spokesman for his family has confirmed.
Ali, who was born Cassius Marcellus Clay Jr, died on Friday. He was hospitalised the day beforehand for treatment for a respiratory issue, although the cause of his death has not been disclosed.
The three-time heavyweight champion of the world had also suffered from Parkinson's disease since 1984.
Some reports have suggested his breathing had been complicated by the neurological disease which had impaired his speech and movement for decades.
His funeral will take place in his hometown of Louisville, Kentucky.
Ali was known as "the Greatest" not only for his incredible feats in the ring, which saw him win the world heavyweight title three times over 14 years, but for his playful and boastful personality and staunch political stands for civil rights.
His impact on American society far transcended the sport of boxing.
In 1967, just three years after he first beat the fearsome Sonny Liston to become world champion, Ali vocally opposed America's war in Vietnam and refused to be drafted into the US military.
For taking such a stance he was stripped of his titles and banned from the sport for four years - a period which many commentators would have been his fighting peak.
Ali had changed his name from Cassius Clay in 1964 after becoming a member of the Nation of Islam, an African American Islamic movement he was introduced to by his friend and civil rights campaigner Malcolm X
Ali regained his world title a decade after beating Liston with an eighth round knock-out of George Foreman in the 1974 "Rumble in the Jungle" in Zaire.
Joe Frazier had handed Ali his first professional defeat three years before, but Ali took revenge in 1974 and in the ferocious "Thrilla in Manila" in 1975.
After losing to Leon Spinks in February 1978, Ali regained his world title at 36 years of age the following September.
He eventually retired in 1981 following consecutive losses to Larry Holmes and Trevor Berbick.