When was Muhammad Ali first lose?

Muhammad Ali first lost on March 8, 1971, in a highly publicized bout against Joe Frazier at Madison Square Garden in New York City. This fight, known as the "Fight of the Century," ended with Frazier winning by unanimous decision after 15 rounds. The loss marked a significant moment in Ali's career, as it was his first defeat after he had been stripped of his title and banned from boxing for refusing military service.