Muhammad Ali refused induction into the U.S. armed forces in 1967 during the Vietnam War.
At the time, Ali was the reigning world heavyweight champion and was eligible for the military draft. On April 28, 1967, he reported for induction in Houston, Texas, but refused to step forward when his name was called. Ali cited his religious beliefs as a Muslim and his opposition to the war.
The refusal brought severe consequences. He was stripped of his boxing titles, denied a boxing license in many states, and convicted of draft evasion. A judge sentenced him to five years in prison, although he remained free while appealing. In 1971, the U.S. Supreme Court overturned his conviction.
A common mix-up is to say Ali was imprisoned immediately; he was not. His conviction stood for several years, but he continued challenging it while barred from professional boxing. The episode transformed him from a sports celebrity into a major figure in debates over race, religion, civil rights, and the Vietnam War.