Deontay Wilder will fight Jai Opetaia on the undercard of Tyson Fury vs Anthony Joshua at the Principality Stadium in Cardiff on December 11.
Unbeaten cruiserweight star Opetaia is stepping up to heavyweight for the first time to box Wilder, a former world champion and renowned as one of the hardest punchers ever in the sport.
In the main event, Fury and Joshua meet in a long-awaited all-British heavyweight fight.
It would be a first high-level heavyweight fight for Opetaia, a previous holder of the IBF championship who has been a force at cruiserweight.
Wilder is now 41 years old but the former WBC titlist is still known for his fearsome punch-power.
Speaking of Opetaia, Dana White, the Australian's promoter, previously told Sky Sports: "It's a very dangerous fight for him considering where he sits in his division right now.
"But he's a fighter; he'll fight anybody, even at heavyweight with a guy who hits as hard as Wilder does."
Opetaia would likely return to cruiserweight afterwards. He and David Benavidez are considered the two best fighters in the 200lb weight class and Benavidez remains Opetaia's ultimate target.
"That's the fight he really wants. He wants that fight so we've got to figure that one out," White said, adding: "He wants to stay active, he wants to fight and he doesn't care if it's at heavyweight or wherever, he's ready to go."
Wilder had an epic trilogy with Fury and came close to setting a fight with Joshua, only to lose to Joseph Parker.
In his last fight, Wilder battled to a points win over British contender Derek Chisora at The O2 in London in April.
Watch Chris Billam-Smith fight Cheavon Clarke on Saturday live on Sky Sports.
