WBA regular bantamweight champion Jamie McDonnell will face Naoya Inoue on the challenger's home turf in Tokyo, Japan on May 25.
McDonnell (29-2-1, 13 KOs) is unbeaten in the last decade but faces a daunting task against Inoue (15-0, 13 KOs), who previously won world titles at light-flyweight and super-flyweight.
McDonnell, 31, said via social media: "So it's on we go to Japan to defend my WBA world title against one of the pound-for-pound best in Naoya Inoue.
"This is why I'm in the game. To be the best you have to fight the best. I am the best bantamweight on this planet and I will prove it again on May 25."
McDonnell's trainer, Dave Coldwell, added: "Huge fight. Yes it's a tough task, but we're not going for the culture! A win in Tokyo and finally Jamie becomes the star his achievements deserve."
McDonnell won the title in May 2014 with a 10th-round stoppage of Tabtimdaeng Na Rachawat at Wembley.