Rio Ferdinand is launching a new career as a professional boxer, two years after he retired from football.
The 38-year-old's move into the ring is being backed by betting company Betfair, which announced the news on Tuesday.
Former Manchester United and England defender Ferdinand works as a TV pundit and he has his own clothing line.
"I'm doing this because it's a challenge," he said. "I've won titles and now I'm aiming for a belt."
He has posted several social media videos in recent months showing him boxing and working with personal trainer Mel Deane.
Ferdinand, who won the Premier League six times and the Champions League once during his time in Manchester, may follow in the footsteps of former Birmingham City midfielder Curtis Woodhouse and former Crystal Palace forward Leon McKenzie, who became professional boxers after quitting football. Woodhouse became British super-lightweight champion.
Former England cricket captain Andrew Flintoff also launched a boxing career after retiring, winning his only pro bout in December 2012 against American Richard Dawson at Manchester Arena on points.
It was Betfair who approached Ferdinand about making the switch, and the betting company will help him qualify for his British Boxing Board of Control (BBBC) licence before he begins training and competing.
The company previously backed Victoria Pendleton in her transition from Olympic cyclist to Cheltenham jockey.
"When Betfair approached me about the challenge, the chance to prove myself in a new sport was a real draw," Ferdinand added.
BBBC general secretary Robert Smith said they had not yet received an application from Ferdinand for a boxer's licence.
"I was completely surprised," he said. "We don't have an application, so there's nothing to consider. Nor have we had any conversation with anybody regarding this."
'It's laughable... he could get himself badly hurt'
Ferdinand will be coached by Team GB coach and former WBC super-middleweight champion Richie Woodhall.
"In all honesty, I think Rio can definitely box as a professional given time. He has natural power in his right hand, is extremely fit and is very enthusiastic to learn which is encouraging," Woodhall said.
"Style wise, he's very raw and I'll have to develop this, which will take time, but he has all the natural ingredients, height and reach advantages over boxers in his weight division and definitely has potential to win a title in the future."
The former centre-back started his career with West Ham and also played for Leeds and QPR, making more than 500 career club appearances. He was capped 81 times for England.
Woodhouse told BBC Radio 5 live he was "shocked" to hear of Ferdinand's career change.
"When it came up on my Twitter feed that Rio Ferdinand was going to become a professional boxer I thought I'd been hacked," he said. "It's not something you read every day is it?
"I've been retired three years myself and one thing I missed - and he's probably going through himself at the minute - is the competitiveness of being an athlete.
"Once that's taken away from you it's very, very difficult to replace it, so that's probably what he's chasing - to get that competitiveness back in his life."
Promoter Barry Hearn said he thought there was only a 50/50 chance that Ferdinand would receive a boxing licence, and told BBC Radio 5 live: "It's laughable. I like Rio, don't get me wrong, but this is an advert for a reality TV show.
"If Tony Bellew, David Haye or Anthony Joshua hit Rio Ferdinand it would probably be prosecutable by the police for using a deadly weapon. He could get himself badly hurt.
"It's OK if it's just a bit of fun, making a TV show and making some money. I wish him luck, I hope he enjoys it but be very careful because it's dangerous.
BBC Sport's Simon Stone
Why is it happening?
Since his retirement in 2015, Ferdinand has been very public about keeping himself in shape through his social media channels.
Sponsors Betfair were aware of this and felt Ferdinand would fit the template they wanted of a former professional sportsman trying another discipline, as they did with former Olympic cyclist Victoria Pendleton, who, 12 months after being set the challenge of becoming a jockey, rode in a competitive race at the Cheltenham Festival in 2016, finishing fifth.
Ferdinand says he is committed to the challenge and has set himself the lofty target of winning a title belt.
His only previous experience of boxing has been as part of his training regime.
If he remains around his footballing weight of 87kg, he would enter in the cruiserweight category.
Ovill Mckenzie, just over a year younger than Ferdinand at 37, has been the British champion since 2014.