Juan Manuel Marquez avenged his two previous defeats to Manny Pacquiao by producing a devastating sixth-round knockout in Las Vegas.
Both men touched the canvas early in the fight, however it was Mexican veteran Marquez who ended the fight in style with a crunching right hand over the top at the end of the sixth.
It was a stunning finish from Marquez, who had been dropped in the fifth round himself after Pacquiao caught him with a powerful left.
The victory improves Marquez's record to 55-6-1 and leaves Filipino former welterweight king Pacquiao's career in major doubt after back-to-back defeats.
The previous three encounters between the two welterweights had not been short of controversy with decisions disputed, but there was no doubt about this one.
After two cagey rounds, it was Marquez who landed the first telling blow in the third. A big right-hander sent Pacquiao to the canvas and, though he bounced straight back up again, it was clear the Filipino was rattled.
A high-octane and even fourth followed, but in the fifth it was Pacquiao who stepped up a gear, landing a big left jab on Marquez, who touched the canvas with his glove.
With Marquez cut and hurting, the 33-year-old scented blood and pressed forward in the sixth.
But in his haste to finish off Marquez he left himself open and the Mexican produced a thundering counter-punch which left Pacquiao face down on the canvas.
Should Manny Pacquiao retire after defeat to Juan Manuel Marquez?