Britain's Fury, who was undecided after the fight about triggering the rematch clause, was the early aggressor but Usyk gradually took charge and the "Gypsy King" was saved by the bell in the ninth round before slumping to his first career defeat.

Ukraine's Usyk, who remains undefeated, joins the likes of Muhammad Ali, Joe Louis and Mike Tyson as undisputed heavyweight champion, the first since boxing recognised four major belts in the 2000s.

With the win, the former undisputed cruiserweight champion can legitimately claim to be the best of this heavyweight era, although a rematch expected in October could provide another twist.

"It is a big opportunity for me, for my family, for my country," said Usyk, 37, who briefly served as a soldier after the Russian invasion.

"It's a great time, a great day," he said, adding that he was "ready for a rematch".

Fury called it a "fantastic fight with Oleksandr" but claimed that sympathy for Ukraine's ongoing war with Russia swung the judges.

"I believe I won that fight, I believe he won a few of the rounds, but I won the majority of them," he said.

"You know his country is at war, so people are siding with the country at war but make no mistake, I won that fight in my opinion and I will be back."

Fury, however, said he would discuss the potential rematch, loosely scheduled for October, with his wife and children.

"I'll have a holiday, go home, put it to the wife and kids, I'll see what I want to do," he told reporters.

"I'm 36 in a few months. I've been boxing since I've been a child so it is what it is."

Britain's Lennox Lewis was the last man to unify the heavyweight belts -- three at the time -- after beating Evander Holyfield in 1999.

It is unlikely that any October rematch would be for all four belts as the IBF plan to strip Usyk if he does not face its mandatory challenger Filip Hrgovic next.

- Fired-up Fury -

Two judges scored it for Usyk by scores of 115-112 and 114-113 while the third gave it to Fury 114-113. The victory extended Usyk's professional record to 22-0. After his first loss, Fury stands at 34-1-1.

Ukrainian President Volodymyr Zelensky, leading the war effort against Russia for more than two years, posted on social media: "Ukrainians hit hard! And in the end, all our opponents will be defeated."

Usyk, who adds Fury's WBC belt to his IBF, WBA and WBO titles, looks set to go down as one of the greats after dominating at amateur, cruiserweight and now the top division.

A fired-up Fury came running out of his corner to start the fight and the 6ft 9ins (2.06m) man was quickly into his rhythm, keeping the shorter Usyk back with his jab and playing to the crowd.

Usyk got inside with some quick combinations while Fury landed some heavy body shots. By round four, the Mancunian was taunting his ever-advancing opponent and showboating, guard down.

Usyk called two low shots in round five and got caught with a left hook as Fury continued to look comfortable, landing a telling uppercut in the following round and bobbing and weaving to stay out of range.

But the Ukrainian tagged Fury with two clean lefts in the seventh and landed a punishing hook that dazed the "Gypsy King" in the eighth.

By the next round, a relentless Usyk barrage had Fury in serious trouble and the wobbling, bleeding Mancunian took a standing count before being saved by the bell.

Fury recovered his poise and with the match in the balance heading into the final round, both fighters were finding the target.

- Ronaldo, Neymar -

Wladimir Klitschko was among the legends watching along with Saudi-based football stars Cristiano Ronaldo and Neymar, who like boxing are grateful beneficiaries of the oil-rich monarchy's lavish push into sports.

Riyadh's newly built, 22,000-capacity Kingdom Arena was packed when Usyk strode out for his ringwalk at 1:30 am (2230 GMT) wearing a green cossack coat and fur hat.

Fury followed, dancing to Barry White and Bonny Tyler's "Holding out for a Hero" in a green sleeveless jacket and back-to-front baseball cap.

It set the stage for a clash of two fighters with impeccable pedigrees and very different approaches to the sport.

Fury has had a rollercoaster career, with lows including a two-year, backdated drug ban and struggles with alcohol, cocaine and depression.

Fury had shed 15lb from his last outing when, sluggish and out of shape, he was knocked down by ex-MMA fighter Francis Ngannou en route to a split decision in October.

Usyk, by contrast, has been the model of consistency with a career that was always on the rise.

The 37-year-old from Simferopol in Crimea put together an outstanding amateur record, winning European and world titles and Olympic gold in 2012.

After turning pro, he unified the cruiserweight belts in 15 fights before moving up to heavyweight, where he took three belts from Anthony Joshua in 2021 and won their rematch the following year.