Anthony Joshua will defend his WBA, WBO and IBF heavyweight titles against Alexander Povetkin of Russia in London on Sept. 22.
Joshua's promoter Eddie Hearn on Monday confirmed the fight, which will take place at Wembley Stadium.
Povetkin is the mandatory challenger to the WBA title. The 28-year-old Joshua has been in training while negotiations with WBC champion Deontay Wilder stalled, but could yet face the American in April 2019.
Joshua said in a statement: "Povetkin is a serious challenge that I will prepare meticulously for. He has serious pedigree and only a fool would underestimate what he brings to the table."
Povetkin, 38, beat David Price on the undercard of Joshua's victory over Joseph Parker in March, having previously fought for the titles Joshua now holds in a 2013 defeat to Wladimir Klitschko.