Nigel Benn and Steve Collins have told BBC Sport they have agreed a rematch – even though neither man has fought since the 1990s and both are over 50.
Benn, 53, and Collins, 52, were once among the biggest names in the super-middleweight division.
Dublin-born Collins has twice beaten Londoner Benn, who retired after their second fight in 1996.
Details of the third fight are yet to be agreed but Benn expects it to take place in October or November.
Benn, nicknamed ‘The Dark Destroyer’, held the WBO middleweight title and the WBC super-middleweight belt before retiring as a fighter following his second defeat by Collins at the Manchester Arena in November 1996.
The Londoner, whose son Conor made his professional debut in April 2016, has talked up the possibility of a return to the ring before.
An attempt to organise a rematch with old rival Chris Eubank came to nothing, but both Benn and Collins have indicated that they are ready to fight each other again.
If the British Boxing Board of Control refuses to sanction the bout, both fighters have said they would seek a boxing licence from abroad.
“It’s about the final chapter,” Benn said. “It’s about closure.
“I was going backwards and forwards with Chris and I thought: ‘I wouldn’t have a problem with Steve.’ So I asked him if he wants to fight. He said yes. No mucking about.”
Collins, who ended Eubank’s unbeaten record to win the WBO super-middleweight title in 1995, last fought in July 1997. An attempt to come out of retirement in 1999 was halted when he collapsed during a sparring session.
The Irishman has also talked of fighting again in recent years, saying in a 2013 interview that he wanted to take on Roy Jones Jr.
Collins, whose son Steve Jr has been a professional boxer since 2013, said his motivations for taking on the fight with Benn were financial.
“It’s just about money, a payday which will allow me to buy some more land,” he said.
“I have no problem for Nigel. I have a lot of respect. I like him.”
Since his retirement, Benn has helped train young boxers, and has also made a career as a DJ – while in 2002, he appeared as a contestant in the first series of ITV’s I’m A Celebrity… Get Me Out Of Here.
He said that he feels in the best shape of his life, comparing himself to Benjamin Button, the F Scott Fitzgerald character who becomes younger in appearance as he gets older.
Benn added that he felt fitter now than he did at his professional peak, a time during which he said he was smoking cannabis and struggling with troubles in his personal life.
“I’m not angry any more and I can have everything I ever want,” he said. “I am Nigel ‘Benjamin Button’ Benn. I feel like I am in my thirties.”
Collins, nicknamed ‘The Celtic Warrior’, has worked as an actor since his last professional fight, appearing in the 1998 film Lock, Stock and Two Smoking Barrels.
He is confident that he will be cleared medically to fight Benn, despite the collapse that prevented his comeback in the late 1990s.
“I am not fighting a 20-year-old-guy,” he said. “I’m fighting someone the same age as me. There’s no disadvantage to anybody.
“I get medicals every year and the most impressive part is my MRI. ‘Excellent’ was how the neurosurgeon described it. I’m very healthy and very fit.”