50 years ago today, 22-year-old challenger Cassius Clay (Muhammad Ali) battered the heavily favored heavyweight champion Sonny Liston in a bout that shook the boxing world. The fight ignited the career of one of sports’ most charismatic and controversial figures, whose bouts often became social and political events rather than simply sports contests. (Neil Leifer/SI)
GALLERY: Muhammad Ali vs. Sonny Liston I
GALLERY: SI’s 100 Greatest Photos of Muhammad Ali

50 years ago today, 22-year-old challenger Cassius Clay (Muhammad Ali) battered the heavily favored heavyweight champion Sonny Liston in a bout that shook the boxing world. The fight ignited the career of one of sports’ most charismatic and controversial figures, whose bouts often became social and political events rather than simply sports contests. (Neil Leifer/SI)

GALLERY: Muhammad Ali vs. Sonny Liston I

GALLERY: SI’s 100 Greatest Photos of Muhammad Ali

James “Buster” Douglas hits Mike Tyson with a hard right in the face during their world heavyweight title bout at the Tokyo Dome in Japan on Feb. 11, 1990.  Douglas came into the fight shaken by the death of his beloved, doting mother, Lula Pearl, who had died while he was training for the fight.  Then undefeated, undisputed heavyweight champion Mike Tyson lost via knockout in the 10th round to the 42–1 underdog Douglas. (Sadayuki Mikami/AP)

James “Buster” Douglas hits Mike Tyson with a hard right in the face during their world heavyweight title bout at the Tokyo Dome in Japan on Feb. 11, 1990.  Douglas came into the fight shaken by the death of his beloved, doting mother, Lula Pearl, who had died while he was training for the fight.  Then undefeated, undisputed heavyweight champion Mike Tyson lost via knockout in the 10th round to the 42–1 underdog Douglas. (Sadayuki Mikami/AP)

"Down goes Frazier!" Howard Cosell’s memorable call provided a dramatic soundtrack to George Foreman’s shocking two-round destruction of Joe Frazier in Kingston, Jamaica, on Jan. 22, 1973. With the win, Foreman claimed the heavyweight title and set himself up as the most feared puncher in the sport.  The former two-time World Heavyweight Champion and Olympic gold medalist turned 65 years old on Jan. 10, 2014. (Neil Leifer/SI)
GALLERY: Neil Leifer’s Iconic Boxing Photos

"Down goes Frazier!" Howard Cosell’s memorable call provided a dramatic soundtrack to George Foreman’s shocking two-round destruction of Joe Frazier in Kingston, Jamaica, on Jan. 22, 1973. With the win, Foreman claimed the heavyweight title and set himself up as the most feared puncher in the sport.  The former two-time World Heavyweight Champion and Olympic gold medalist turned 65 years old on Jan. 10, 2014. (Neil Leifer/SI)

GALLERY: Neil Leifer’s Iconic Boxing Photos

Mike Tyson forces Michael Spinks to take a knee a minute into their fight on June 27, 1988, in Atlantic City, NJ.  It was the first time Spinks had been knocked down in his professional career. Spinks took a count of four before rising, only to be knocked down again shortly thereafter. The fight was over after 91 seconds. (Neil Leifer/SI)
GALLERY: Tyson vs. Spinks: 25th Anniversary

Mike Tyson forces Michael Spinks to take a knee a minute into their fight on June 27, 1988, in Atlantic City, NJ.  It was the first time Spinks had been knocked down in his professional career. Spinks took a count of four before rising, only to be knocked down again shortly thereafter. The fight was over after 91 seconds. (Neil Leifer/SI)

GALLERY: Tyson vs. Spinks: 25th Anniversary