On January 22, 1973, Foreman faced undefeated world Heavyweight champion Joe Frazier in Kingston, Jamaica, knocking him down no less than six times in two rounds and knocking him out in the second round in one of boxing history's biggest upsets to become the world champion. In what was HBO Boxing's first transmission ever, the call made by Howard Cosell, the broadcaster that night ("Down goes Frazier!, Down goes Frazier!, Down goes Frazier!") became one of the most memorable sports calls of all time. Equally memorable was Foreman's final punch, an uppercut landed with such force that it lifted Frazier off his feet before sending him to the canvas. As he had done following the five previous knockdowns, Frazier got up, but this time the referee sensibly stepped in to end the slaughter.

(From Wikipedia)