An historic undisputed heavyweight fight between champions Tyson Fury and Oleksandr Usyk has been signed and will take place in Riyadh, Saudi Arabia.
Additional details, including the fight date, are yet to be announced.
Briton Fury, 35, is the WBC champion and Ukraine's Usyk, 36, holds the WBA, WBO and IBF titles.
"Delighted to finally get this fight signed. This is the biggest fight that could possibly be made in our sport," said Queensberry promoter Frank Warren.
The winner will be crowned the first undisputed heavyweight champion in the four-belt era.
The targeted date is 23 December, although the fight could be pushed back to early next year.
Fury has won 33 fights with one draw since turning professional in 2008.
'The Gypsy King' must first come through a non-title bout against MMA star Francis Ngannou uninjured on 28 October in Riyadh.
Usyk - who has won all 21 pro bouts - defended his titles against Londoner Daniel Dubois in August.
"The heavyweights always spark the imagination of the fans, and I have no doubt this will be the biggest boxing event of the century," Warren added.
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Fury faced criticism for failing to reach terms with Usyk after a proposed bout at London's Wembley Stadium in April fell through.
"I can't believe that it's happening but it is," Usyk's promoter Alexander Krassyuk said.
There has not been an undisputed heavyweight champion since 1999 when Lennox Lewis beat Evander Holyfield to defend the WBA, WBC and IBF titles.
"Tyson Fury and Oleksandr Usyk are the two greatest heavyweights of their generation, and I can't wait to see what happens when they step into the ring in Riyadh," Fury's co-promoter Bob Arum said.
"They are special talents worthy of competing for the greatest prize in sports."
The fight will form part of 'Riyadh Season' - an entertainment events festival held in Saudi Arabia's capital every winter since its launch in 2019.
A number of high-profile bouts have been held in Saudi in recent years, including Usyk's win over Anthony Joshua in August 2022.
The Gulf kingdom has been accused of investing in sport and using high-profile events to improve its international reputation.
Saudi Arabia has been criticised for its human rights violations - 81 men were executed on one day last year - women's rights abuses, the criminalisation of homosexuality, the restriction of free speech and the war in Yemen.
Its international standing was severely damaged by the 2018 killing of Jamal Khashoggi, a US-based Saudi journalist who was a prominent critic of the government.
Human rights campaigners say sport is being used by the Saudi government to distract from long-standing reputation issues.
Felix Jakens, Amnesty International UK's Head of Priority Campaigns and Individuals at Risk, said in a statement: "Ever since Anthony Joshua's fight against Andy Ruiz in 2019 we've become used to these big-money bouts being hosted in Saudi Arabia.
"They are clearly part of a pattern of sportswashing where the Saudi authorities try to use sport to distract from their appalling human rights record.
"We'd like to see both Tyson Fury or Oleksandr Usyk using their platforms to speak out about human rights issues in Saudi Arabia."
Fury won his first world title after dethroning Wladimir Klitschko in 2015, before takin a hiatus from the sport.
After well-documented issues with mental health, he returned more than two and a half years later. He contested a trilogy with Deontay Wilder and, having drawn the first fight, beat the American in 2020 to become WBC champion.
Fury won the third fight with hard-hitting Wilder and has since defended his belt against Britons Dillian Whyte and Derek Chisora.
Usyk is one of the most decorated fighters in world boxing. The London 2012 Olympic gold medallist became undisputed world champion before dethroning Briton Joshua in 2021.
Analysis - the winner will earn greatness status
It is the announcement everybody wanted but nobody expected, especially just before close of play on a Friday. The biggest possible fight in world boxing has been signed. Fury and Usyk have put their differences aside. It does not get bigger than this.
For so long boxing lovers have been left frustrated with the state of the heavyweight division. Why aren't the best fighting the best? Fury's fight with Ngannou - a boxing novice - in particular left a bad taste.
But now we can finally get the answer as to who is the top heavyweight boxer in the world. Fury and Usyk will both one day enter the hall of fame. The winner of this fight, however, will earn greatness status.
There will still be some wondering why there is no date. Both sides are aiming for 23 December, but that will leave Fury just eight weeks to prepare after his 'fight' with Ngannou.
Riyadh season runs until March so it could take place at any point over the next six months. Some may remain sceptical all the way up until both men are in the ring and the first bell chimes.
