Oleksandr Usyk will defend his IBF, IBO, WBO and WBA heavyweight titles against Britain's Daniel Dubois next month.
The match will take place at the Tarczynski Arena in Wroclaw, Poland, on August 26.
Usyk was expected to fight WBC world heavyweight champion Tyson Fury in a unification fight but negotiations fell through in March.
Dubois, 25, is the WBA (regular) heavyweight belt holder and mandatory challenger.
Former undisputed cruiserweight champion Usyk snatched the titles off Anthony Joshua in London in September 2021 and won the rematch in August last year in Saudi Arabia.
Dubois will be Usyk's second defence of his world heavyweight belts with the match-up announced on Twitter by Frank Warren's Queensbury Promotions.
Usyk, whose scheduled showdown with Tyson Fury at Wembley fell through due to contractual disputes, said simply on Instagram: "See you 26 August".
Londoner Dubois, nicknamed 'Dynamite', has won 19 of his 20 fights since turning professional in 2017, 18 by knockout, with one defeat, against fellow British heavyweight Joe Joyce in 2020.
Dubois suffered a fractured orbital bone and nerve damage to his left eye when stopped in the 10th round by Joyce, but has beaten four opponents since.