Born Cassius Marcellus Clay in Louisville, Ky., in 1942, Muhammad Ali is an American boxer who was the first to win the heavyweight championship three separate times. He won an Olympic gold medal in Rome in 1960, going on to become the world heavyweight champion in 1964 by defeating Sonny Liston, who retired after six rounds.
In 1964 Ali converted to Islam, at that time taking on the name Muhammad Ali. In 1967 he refused, on religious grounds, to submit to induction into the armed forces. He was subsequently arrested, barred from the ring, and stripped of his heavyweight title, although the conviction was eventually overturned by the U.S. Supreme Court.
Ali went on to fight other title contenders, and in Kinshasa, Zaire (now the Democractic Republic of the Congo) in 1974 he won an eight-round knockout of George Foreman, regaining the undisputed world heavyweight title.
In the 1980s, when Ali was in his 40s, he was diagnosed with chronic encephalopathy of boxers, which is characterized by parkinsonian symptoms -- slurred speech, facial immobility, poor balance, and difficulty walking. He has since used his celebrity stature to raise awareness and funds for Parkinson's research and study.