Carl Froch will defend his IBF and WBA world super-middleweight titles against fellow Englishman George Groves.
The bout will be in either late November or early December at a venue which is yet to be announced.
"I've known George for a while. I've sparred with him and watched him grow and now he's my mandatory," said 36-year-old Froch.
"I will be pouring everything into my preparation for the fight and George will face the very best of me."
Froch beat Mikkel Kessler to add the WBA title to his IBF crown in May and he has won 31 of his 33 fights - 22 by knockout.
Groves, 25, was on the undercard of that Froch-Kessler fight and knocked out Uruguay's Noe Gonzalez Alcoba to become the mandatory challenger to Froch's IBF title.
"I'm excited the first defence of both my belts is a big domestic clash," said Froch.
"I am a proper fighter and a proper champion and I will always face my mandatory challenger rather than vacate the title."
Groves is unbeaten in 19 fights and his wins include 15 knockouts.
He sparred with Kessler before his fight against Froch, who was unhappy a fellow Briton was aiding a foreign opponent.
"This is the biggest fight of my career and being a world champion is something that I dreamed of as a kid," said Groves.
"I'm well ranked across all the governing bodies but fighting Carl is the one that I wanted the most. He is a big name in the UK and a well-respected champion around the world.
"I have a great team around me that can put together the right game plan to beat him and become a world champion and a major force in the super-middleweight division."