The "Thrilla in Manila" lasted 14 rounds before it was stopped.
Muhammad Ali and Joe Frazier fought for the undisputed heavyweight championship at the Araneta Coliseum in the Philippines on October 1, 1975. The bout was scheduled for 15 rounds, as was customary for major heavyweight championship fights at the time, but the final round never began.
After the 14th round, Frazier’s chief second, Eddie Futch, decided to stop the contest. Frazier’s eyes were badly swollen and his ability to see Ali had deteriorated. Futch later explained that he did not want to risk sending his fighter into another round under those conditions. Ali therefore won by corner retirement, rather than by a knockout or a referee’s stoppage during a round.
The number 15 is the most natural alternative people remember because the fight was scheduled for 15 rounds. Another common mistake is saying 12 rounds, the distance used in many modern championship bouts. Ali was also exhausted and reportedly told his corner that he could not continue, which shows how close the fight came to lasting the full scheduled distance.