Muhammad Ali (born Cassius Clay, 1942)
Within 6 years of taking up boxing, Clay had become the Olympic Light Heavyweight champion in 1960, but threw his medal away in disgust at the way he was, even as an acclaimed sportsman, treated by segregated America.
Four years later he became heavyweight champion of the world and converted to Islam, dropping his ‘slave-name’.
Ali continually stressed the importance of upholding principles, refusing on political grounds to fight in the Vietnam War, even when his medals were stripped from him.
Ali thereafter won his championship status back and has been world champion three times.
He is often acknowledged as the greatest boxer ever.