Daniel Dubois defeated Anthony Joshua by fifth-round knockout on Saturday to retain his IBF heavyweight title.
Dubois produced a stunning performance in front of a sellout crowd of 96,000 at Wembley Stadium in London.
The 27-year-old knocked down Joshua four times and finished him off in the fifth round with a right to the chin.
This latest defeat represents a huge setback for Joshua, who was in position to secure a likely fight against the winner of the December 21 bout between Oleksandr Usyk and Tyson Fury.
Dubois will get that shot after improving to 21-3.