LAS VEGAS — So that's why every welterweight in the world was so scared of Antonio Margarito.

Margarito stopped Miguel Cotto in the 11th round tonight, blemishing Cotto's unbeaten record and claiming the WBA 147-pound title with one last incredible barrage of punches.

Margarito (37-5, 27 KOs), the Mexican star so often ducked by the division's best fighters in recent years, dropped the Puerto Rican champion twice in the 11th after several rounds of relentless pressure in a fight that lived up to its lofty billing at the MGM Grand Garden.

"I told my corner I would wear him down and then knock him out," said Margarito, who won his third welterweight belt. "He never hurt me, but that was the game plan, to come out early strong and to wear him down and knock him out. I got him with body shots, and then I hit him in the head, and then I knocked him out."

Cotto (32-1), the respected champion attempting his fifth title defense, won the early rounds with defense and timely counterpunching. Margarito took several major shots on his tough chin, yet still kept up the same relentless attack that finally paid off in the middle rounds.

With Cotto bleeding and woozy, the champion's corner stopped the fight with 55 seconds left, sending Margarito's team into a delirious celebration of a long-awaited victory. Cotto, unable to speak clearly through tears and welts, was taken to a hospital from his locker room.

"I am very proud and very happy I was able to give the fans a great fight," Cotto said. "Life continues. It's not over for me. I'm going to take a long rest, decide what to do next. This night was Margarito's night. He's an excellent fighter. He did his job better than I did."

From the opening round, the fight matched every expectation in the Mexico-Puerto Rico rivalry that has produced innumerable memorable fights in the last three decades. Their countrymen filled the arena with cheers, flags and chants, but Margarito had more passion — perhaps because his motivation was several years in the making.

Margarito has long been a looming nightmare for the division's top fighters because of his heedless style and tough chin. Floyd Mayweather Jr. turned down an $8 million payday to avoid facing the "Tijuana Tornado" in 2006 — a dodge that resonated with Cotto, who also couldn't get the Pretty Boy to return his promoters' calls.

This fight came together in April when Cotto and Margarito trounced two challengers on the same card in Atlantic City. Promoter Bob Arum immediately gave both fighters the matchup they craved, putting his two top welterweights together for a joint debut as Vegas headliners — though Cotto made $3 million to Margarito's $1.5 million.

The loss clearly stunned Cotto, who had shown remarkable resourcefulness after being staggered in two 140-pound fights. Though Cotto carried the early action, Margarito bloodied Cotto's nose and mouth before picking at the wounds throughout the middle rounds.

Margarito, who took three of his five career losses as a teenager in Mexico, lost his WBO welterweight title to Paul Williams last year with an uncharacteristically slow start. He claimed the IBF title three months ago by battering Kermit Cintron, but had to give up that belt to make the match with Cotto — a gamble that paid off immensely.