Ruslan Provodnikov stopped Mike Alvarado inside 11 rounds to capture the WBO world light welterweight title in Colorado on Saturday night.
The Russian fighter, nicknamed the "Siberian Rocky", knocked down American Alvarado twice in the eighth round with a series of punches near the ropes and finished him off late in the 10th.
Alvarado made it to the bell but did not return from his seat at the start of the 11th round.
The victory takes Provodnikov's record to 23-2 and puts the disappointment of his defeat to Timothy Bradley back in March firmly behind him.
After the fight, Alvarado admitted that Provodnikov threw the hardest punches he has ever encountered. He also revealed that manager Henry Delgado stopped the fight and that he agreed with the decision.
"It was not worth taking more punishment because the damage could be permanent," Alvarado said. "It just wasn't my night. I have a lot of heart. I'm not a quitter."
Provodnikov, who could next fight the winner of Manny Pacquiao and Brandon Rios, was delighted with his display.
"My team told me, 'You're ready, come out and become a champion," he said.
"If you want to be a world champion, you have to risk it - go and fight the best, go to his hometown."