Muhammad Ali (/li/; born Cassius Marcellus Clay, Jr.; January 17, 1942) is an American former professional boxer, generally considered among the greatest heavyweights in the history of the sport. A controversial and polarizing figure during his early career, Ali is now highly regarded for the skills he displayed in the ring plus the values he exemplified outside of it: religious freedom, racial justice and the triumph of principle over expedience. He is one of the most recognized sports figures of the past 100 years, crowned Sportsman of the Century by Sports Illustrated and Sports Personality of the Century by the BBC.Ali began training at 12 years old and at the age of 22 won the world heavyweight championship in 1964 from Sonny Liston in a stunning upset. Shortly after that bout, Ali joined the Nation of Islam and changed his name. He converted to Sunni Islam in 1975.In 1967, three years after winning the heavyweight title, Ali refused to be conscripted into the U.S. military, citing his religious beliefs and opposition to American involvement in the Vietnam War. He was eventually arrested and found guilty on draft evasion charges and stripped of his boxing title. He did not fight again for nearly four yearslosing a time of peak performance in an athlete's career. Ali's appeal worked its way up to the U.S. Supreme Court, where in 1971 his conviction was overturned. Ali's actions as a conscientious objector to the war made him an icon for the larger counterculture generation.Ali remains the only three-time lineal world heavyweight champion; he won the title in 1964, 1974, and 1978. Between February 25, 1964 and September 19, 1964 Muhammad Ali reigned as the undisputed heavyweight boxing champion.Nicknamed The Greatest , Ali was involved in several historic boxing matches. Notable among these were the first Liston fight, three with rival Joe Frazier, and one with George Foreman, where he regained titles he had been stripped of seven years earlier.At a time when most fighters let their managers do the talking, Ali, inspired by professional wrestler Gorgeous George Wagner, thrived inand indeed cravedthe spotlight, where he was often provocative and outlandish. He controlled most press conferences and interviews, and spoke freely about issues unrelated to boxing. He transformed the role and image of the African American athlete in America by his embrace of racial pride and his willingness to antagonize the white establishment in doing so. In the words of writer Joyce Carol Oates, he was one of the few athletes in any sport to define the terms of his public reputation .