Tony Bellew's shot at becoming the first Briton to hold four world titles in a weight division ended in failure as Oleksandr Usyk produced a stunning finish in the eighth round at Manchester Arena.
The Ukrainian, initially cautious and behind on the cards, found rhythm around the midway point and, after following a jab with a brutal left hook, he was already smiling as Bellew tried to get back to his feet, to no avail.
Usyk's IBF, WBO, WBA and WBC world cruiserweight titles were safe, despite Bellew's solid counter-punching early on, when the undefeated and undisputed champion struggled with the Briton's movement.
Referee Terry O'Connor waved the bout off and while 35-year-old Bellew appeared dazed in the moments after, he quickly stated he had given "everything" he had.
It was a conclusive finish, befitting of a much-hyped champion, who is now expected to chase the glamour names of the heavyweight division.
"He is just so hard and so awkward. He is big and he overpowers you. I tried my best and he is probably the best cruiserweight that ever lived," Bellew told BBC Radio 5 live.
"It is heartbreaking because I gave it everything I had. Heavyweights stay away, he takes a great shot and I don't even know if I hurt him."
Bellew confirmed it would be his last fight, saying: "I have been doing this for 20 years, and it is over."