INGLEWOOD, Calif. -- Michael Bisping was supposed to just be happy to be there.

His short-notice UFC 199 shot at Luke Rockhold's middleweight title was supposed to just be a reward for a decade's worth of hard work. He wasn't actually supposed to win the main event at the Forum on Saturday night.

But the pride of Manchester, England scored a stunning upset, scoring a first-round knockout of the overconfident Rockhold and implausibly winning the title. The time of the finish was 3:36.

"I gotta be humble, even though I want to be an a**hole," said the 37-year Bisping. "Thank you all for being here. I have always been a fighter."

Rockhold (15-3), who came into the fight with a strained MCL, nonetheless threw kicks from the outset. But that didn't keep Bisping from closing the distance. He dropped Rockhold with a huge left hand to the jaw. Rockhold rolled with it and got back to his feet, only to be met with another big left.

This time, Bisping unloaded with lefts and rights on Rockhold, who was in a sitting position against the cage, until referee John McCarthy waved off the bout at the 3:36 mark.

With the victory, Bisping, who took the bout on 17 days' notice when Chris Weidman had to drop out with an injury, won his fourth straight fight and avenged a 2014 submission loss to Rockhold.

Rockhold, to his credit, made no excuses after having a five-fight win streak snapped.

"Congrats to Michael," said Rockhold. "I didn't see it happening, I took it for granted. I could have capitalized and fought my fight, but I didn't."