Anthony Joshua will return to Cardiff to face Joseph Parker in a boxing world heavyweight title unification fight at the Principality Stadium on March 31.
Joshua's promoters Matchroom Boxing confirmed the deal on Sunday, concluding weeks of fractious negotiations between the two sides.
Joshua will put his WBA and IBF titles on the line against New Zealander Parker, who has held the WBO version of the title since December 2016.
"It is a unification heavyweight championship fight," Joshua said.
"We all know what happened last time I was in a unification heavyweight championship fight - it was gruelling, it was interesting and we both left the ring with masses of respect.
"These fights aren't easy because there is a lot on the line, so respect to team Parker for taking the challenge. I am looking forward to it, training camp is under way and before you know it March 31 will be upon us."
Joshua unified the WBA and IBF titles with his famous win over Wladimir Klitschko last April, before subsequently battling out a late stoppage win over Carlos Takam in Cardiff in October.
The 26-year-old Parker had made his UK debut one month previously, when he earned an underwhelming majority points verdict over challenger Hughie Fury at the Manchester Arena.
"Anthony Joshua is in for a huge shock," Parker said.
"A couple of months ago I heard him say 'why should I be worried about this little kid from New Zealand'?
"Well, now he's about to find out. And the world is about to find out whether AJ can really take a punch. My entire existence is now devoted to proving what the boxing world already knows."
