LOS ANGELES - Boxing legend Floyd Mayweather and mixed martial arts champion Conor McGregor - the kingpins of their respective sports - announced Wednesday they would fight on August 26 in Las Vegas.
The 40-year-old Mayweather announced the fight on his Instagram account with a graphic saying "IT'S OFFICIAL!!!" showing pictures of both fighters and listing Las Vegas as the location.
McGregor sent out a tweet stating "THE FIGHT IS ON." He also included photos of the pair.
MMA promoter Dana White said the bout would take place at the T-Mobile Arena and it would be a boxing match at 154-pounds with 10 ounce gloves.
"We have been in negotiations for a while," White told American sports broadcaster ESPN.
"The negotiations went smooth. Floyd Mayweather surrounds himself with smart people and we got the deal done."
McGregor is the top pay-per-view draw in UFC while Mayweather had been the moneyspinner in some of boxing's biggest bouts, including matchups with Filipino legend Manny Pacquiao and US star Oscar De La Hoya.
Mayweather earned $250 million for his fight against Pacquiao. Neither Mayweather or McGregor have competed this year.
Mayweather retired from pro boxing in 2015 after defeating Andre Berto, while McGregor (21-3) defeated Eddie Alvarez in November 2016.
White said the key to finalizing the fight was luring Mayweather out of his 23-month retirement.
"Everybody is happy with this deal," White said. "Nobody is bummed out."
The boxing format heavily favours the undefeated Mayweather (49-0, 26 KOs) who many consider to be the best pound-for-pound fighter in the world.
McGregor, a 28-year-old Irishman, will be entering unknown territory as he has not stepped in a boxing ring since he was a teenager.
Despite having little or no boxing experience, White insists his MMA client McGregor is confident of victory. McGregor is UFC's only simultaneous two-division champion.
"He is absolutely, 100 per cent positive he will win this fight. When two men step into the ring anything can happen," White said of southpaw McGregor.
There will, of course, be no titles on the line, but it is an opportunity for both to cash in financially.
The fight is expected to be a pay-for-view blockbuster, as organizers are hoping it can challenge the 4.6 million pay-per-view buys for Mayweather-Pacquiao.
Not everyone will be excited to see a Mayweather-McGregor exhibition match, especially considering that McGregor is a 25-1 underdog.
Boxing champion turned promoter De La Hoya said a fight between the two would be an embarrassment for the sport of boxing.
But the trash-talking Irishman has a dedicated fan base and knows how to sell tickets.
In his last fight, McGregor won the lightweight title from Alvarez in November 2015 in UFC's first Madison Square Garden card.
At one time promoters were looking at a September 16 date for Mayweather-McGregor but it is now taken by a Canelo Alvarez-Gennady Golovkin middleweight world championship fight at T-Mobile Arena.
McGregor received a California boxing license last year but is still waiting for his Nevada boxing license application to be approved.