NEW YORK -- Already on the short list of the greatest fighters in UFC history, Georges St-Pierre returned from a lengthy retirement on Saturday to remind of his greatness.

Defying age and cage rust, St-Pierre moved up to middleweight and further etched himself into the history books with a dramatic third-round submission of 185-pound champion Michael Bisping in the main event of UFC 217 at Madison Square Garden.

"I don't have a word in my mouth right now," St-Pierre said. "It's my dream come true."

Four years after walking away from the sport amid personal issues, mental fatigue and displeasure with the UFC's drug-testing protocols, GSP exited the cage in good company.

St-PIerre, who made nine defenses of his welterweight title from 2008 to 2013, joined fellow mixed martial arts legends Randy Couture, BJ Penn and Conor McGregor as the only two-division champions in UFC history.

Bisping, 38, himself coming off a 13-month layoff, was game throughout and bloodied GSP's face in Round 3 with a series of short elbows from his back on the canvas. He also traded evenly throughout on the feet as the two veterans put forth a technical display of defensive counter boxing.

"He hurt me very hard," St-Pierre said. "A few times I got stung and he hurt me but I tried to hide it. I wouldn't want to do that fight again."

But St-Pierre, 36, saved his best for last and showed he had enough juice left to finish strong. A perfect counter left hand in Round 3 floored the champion and GSP leaped to the canvas to flurry with hammer shots on top.

Referee "Big" John McCarthy gave the typically durable Bisping a long leash to survive but once St-Pierre took his back, the fight was over. Refusing to tap, Bisping passed out via rear-naked choke as McCarthy called off the fight at 4:20 of Round 3.

"I studied a lot of Michael's tape and I knew he had problems with the shot coming to his right so our plan was to take him on his left side to distract his attention and strike him on the right," St-Pierre said. "In MMA sometimes, before a few years ago, I was always trying to force things. I think the best way in fighting is to set up some straps so when your opponent steps in them, it's easier to get them."

Bisping, who did his best to sell the fight by constantly berating St-Pierre throughout the promotion, showed nothing but respect after the fight.

"You've got to give it up to Georges, he was the better man tonight," Bisping said. "I said a few things and was just trying to be entertaining. But listen - Georges was the better man. Hell of a f------ squeeze he has got there. Give it up to Georges. Not much else to say.

"I'm not done [fighting even though] I spoke about retirement but Georges was the better man tonight. No excuses. He drove me out and congratulations."

St-Pierre looked big and muscular in his middleweight debut and was 3-for-3 on takedown attempts against the larger Bisping. After the bout, GSP never quite committed to whether he would stay at 185 pounds, where Robert Whittaker holds the division's interim title.

"This is not really my real weight, I did it for my challenge," St-Pierre said. "There was a time in my career that I was too busy with one challenge after another. I was too small to fight at this weight but now I've put on muscle mass and I am comfortable here. I decided to take a shot because I took on some muscle mass.

"It's about marital arts. It's not about who has the biggest balls. It's about technique and setting a trap with diligence. I was trying to prove that for my fans."

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