Anthony Joshua and Tyson Fury will contest their long-awaited all-British heavyweight fight at Cardiff’s Principality Stadium on 11 December.
The bout, more than a decade in the making, will be broadcast globally on Netflix.
BBC Sport understands the main event could take place in the early hours of Saturday morning in the UK, with organisers considering a late start to cater for audiences in the United States.
Joshua and Fury will come face-to-face at a news conference in London on Wednesday, 30 September, as the build-up begins to one of the most anticipated fights in British boxing history.
“I am inspiring a generation,” Joshua, 36, posted on Instagram. Fury is yet to comment on the announcement.
The event is being promoted as a collaboration between Saudi boxing powerbroker Turki Alalshikh’s The Ring and UFC chief Dana White.
“Two of the best heavyweights of this generation, finally in the ring together,” Alalshikh said.
“This will be one of the biggest fights in boxing history. I am very happy to make this fight happen for the fans.”
The former two-time world champions had already signed contracts for the bout earlier this year, but the date and venue had yet to be confirmed.
London’s Wembley Stadium and New York’s Madison Square Garden were the frontrunners to stage the fight, but both presented issues before Cardiff recently emerged as an alternative.
The Principality Stadium has hosted late-night boxing before, including Joe Calzaghe’s fight with Mikkel Kessler in November 2007, which began at 01:00 GMT.
Welsh Rugby Union and Cardiff Council officials welcomed the fight, saying it would reinforce the city’s reputation for staging major events and could bring a significant economic boost, although some operational details still need to be finalised.
Joshua had been pushing for the fight to take place in the UK and has got his wish.
“Forever indebted to the UK public for their support of Anthony Joshua. We couldn’t have got this over the line without you,” his promoter Eddie Hearn said.
It is notable that White, who fronts Zuffa Boxing, is involved in the promotion.
“For more than a decade, boxing fans have been clamouring for the heavyweight showdown between Tyson Fury and Anthony Joshua. Together, they bring 66 wins, 52 knockouts and multiple heavyweight world titles into the ring,” White said.
“On December 11, two of the biggest heavyweights of this generation finally collide – and the winner will take a significant place in heavyweight history.”
There was no official statement from Hearn or Fury’s promoter Frank Warren in the official news release sent by Netflix. Hearn had previously said he did not want White to be involved in promoting the fight.