Anthony Ogogo lost his unbeaten record as fellow Briton Craig Cunningham won the vacant WBC international middleweight title in Birmingham.
The 2012 Olympic bronze medallist, who had won his previous 11 pro fights, never recovered from being knocked down by a right hook in the second round.
Ogogo was retired by his corner in the eighth with blurred vision.
Also on the card, Sam Eggington stopped Frankie Gavin to claim the vacant WBC international welterweight title.
Eggington knocked down his fellow Brummie in rounds three and six and frequently had his opponent hemmed in on the ropes.
Gavin took a barrage of punches in the eighth round and sunk to his knees before the referee intervened to stop the fight.
Cunningham, who has lost just one of his 18 bouts, was a 20-1 outsider with some bookies to beat Ogogo at the Birmingham Arena.
But Ogogo was struggling long before the end as he had no answer to the 28-year-old’s powerful combinations and accurate jabbing.
Cunningham said: “I love being the underdog. Nothing fazes me.
“I had to check how quick he actually was. I fancied myself as a counter-puncher.
“My knockout record isn’t great but if I catch someone, they’re going to go.”