Marquez knocked Pacquiao at the end of the sixth round Saturday night at the MGM Grand in Las Vegas to offer a convincing finish of what is likely the conclusion of a competitive rivalry.
The knockout was just one major development in an action-packed fight. Pacquiao was knocked down in the third round, but was able to rally and knock Marquez down in the fifth.
The sixth round saw both welterweights battle with power punches that did major damage. Marquez was able to land a hard right that floored Pacquiao face down with one second left. The Filipino star was down for nearly two minutes before he got up.
"I threw a perfect punch," Marquez said. "I knew Manny could knock me out at any time."
The victory is perhaps a defining moment in Marquez's career. The 39-year-old lost to Floyd Mayweather in 2009, and had lost all three previous bouts with Pacquiao.
Both boxers are nearing the end of their careers. Pacquiao has previously expressed interest in retirement, making Saturday's result all the more poignant.
"I did my best, but that's boxing," said Pacquiao. "That's sports."
Pacquiao earned more than $20 million for the fight, and was ahead 47-46 on all three scorecards after the fifth round.