Oleksandr Usyk knocks out Daniel Dubois in nine after low blow controversy
Puerto Rican referee Luis Pabon counted out Dubois after he went down 48 seconds into the ninth round at the open-air Tarczynski Arena in Wroclaw, Poland.
Dubois was also given a nine count at the end of the previous round but the key moment came in round five when Usyk, now with a record of 21-0, went down gasping for breath after being hit on the band of his shorts.
The referee ruled it a low blow and told Usyk to take his time as he remained on the canvas grimacing and shaking his head, with the round eventually continuing.
Dubois, who lasted longer than expected but took some big blows with blood oozing from his nose early in round nine, said the blow was legal.
"I've been cheated out of victory tonight," he told TNT Sports in the ring.
His promoter Frank Warren agreed with the fighter and called for a rematch.
"That referee got it badly wrong. If it's a low blow why didn't he take points off him. I like Usyk but that was a home town decision, a complete home town decision. He (Dubois) won that fight.
"They gave him a couple of minutes to recover from a legitimate shot.
"The governing bodies will have to do something about it and they will order a rematch," he added. "How can you not order a rematch on the strength of that? They have to. Justice has to be done."
Usyk had been in control of the fight against a 25-year-old regarded by most as an underdog for whom victory would have ranked as a major upset.
The Ukrainian said he was now ready to fight WBA heavyweight champion Tyson Fury if the Briton was willing.
"Will Tyson Fury? I have no idea," said the winner after dancing in the ring as his fans cheered.
Dubois's chance came after a bout to unify the titles fell apart last March.
Russia's invasion of neighbouring Ukraine hung over the evening, with seven Ukrainians on the undercard and a pre-fight video address from Ukrainian president Volodymyr Zelenskiy to a stadium decked out in the country's yellow and blue colours.
"Tonight Wroclaw will witness something very special," Zelenskiy told the 40,000-strong crowd gathered on a rainy evening.
"Ukrainians, Brits, Poles and the whole world tonight on the eve of the 550th day since the full-scale Russian invasion has started and we keep standing and Ukraine is fighting because of the strength you'll see.
"The strength of our people as mighty as Oleksandr Usyk, the strength of our friends as solid as Daniel Dubois."