A fight which looked like it was going to be decided by the judges was ended by a devastating left hook and then right hand from Canelo Alvarez on Saturday night in Las Vegas.
It had been a fairly uneventful bout between the 29-year-old Mexican and Russian Sergey Kovalev until there was just under a minute left in the 11th round.
That was when Alvarez rocked his 36-year-old opponent with a left hook and sent him crashing to the ropes with his right.
Canelo, who has been ahead on two of the judge's scorecard's before the knockout, stepped up two weight divisions to take on Kovalev. The KO won him the WBO light heavyweight title and means he has now won belts in four divisions.
The victory was the 53rd of his career. His sole defeat was six years ago against Floyd Mayweather.
Asked post-fight what if his next match would be a trilogy fight against Gennady Golovkin, Alvarez did not rule it out.
"It's not a challenge for me," he said.
"We fought 24 rounds and I beat him. But if it represents business, then why not?"