Bermane Stiverne clinched the vacant WBC heavyweight title after stopping Chris Arreola in the sixth round of their clash in Los Angeles.
Stiverne beat Arreola on points a year ago but this time finished the job inside the distance to succeed the retired Vitali Klitschko as the owner of the belt.
Arreola was dropped twice in the sixth and was taking further punishment when referee Jack Reiss stepped in to stop the fight.
Canadian fighter Stiverne had not fought since his first win against Arreola, while his opponent had knocked out Seth Mitchell in the intervening period.
"I studied and studied. I watched my opponent. I knew I could knock him out,” Stiverne said.
“I was patient. The plan was to let him get comfortable, and he soon as he gets real comfortable, then crack him. And that's what I did."
Home town favourite Arreola was sent to the canvas for the first time by a right hand and although he managed to beat the count, he never fully recovered.
Arreola said: "He has a tremendous right hand, that's exactly what it was. I felt like I was winning the fight. He just got me with the same right hand. Couldn't get away from it, and after that, it's all she wrote."
Stiverne becomes the first fighter of Haitian descent to win the heavyweight title and break the monopoly the Klitschkos held over the division. Vitali’s brother Wladimir still holds the other three versions of the world title.
Stiverne, whose mandatory challenger is the unbeaten American knockout artist Deontay Wilder, says he is not yet thinking about his next fight.
"With all due respect, I don't give a damn about Wilder or Klitschko right now. Right now, it's about what I won,” Stiverne said.