From Wikipedia

 Muhammad Ali - The Greatest

Originally known as Cassius Clay, Ali changed his name after joining the Nation of Islam in 1964, subsequently converting to Sunni Islam in 1975 and more recently to Sufism. In 1967, Ali refused to be inducted into the U.S. military, based on his religious beliefs and opposition to the Vietnam War. He was arrested and found guilty on draft evasion charges, stripped of his boxing title, and his boxing license was suspended. He was not imprisoned, but did not fight again for nearly four years while his appeal worked its way up to the U.S. Supreme Court, where it was successful.