The fight is scheduled for August 26 at the T-Mobile Arena in Las Vegas after months of negotiations.
Mayweather, 40, retired from pro boxing in 2015 after defeating Andre Berto, while McGregor (21-3) beat Eddie Alvarez last November.
The fight is expected to be a 12-round boxing match, with 10-ounce gloves.
When Mayweather steps into the ring against the UFC fighter in Las Vegas on August 26, he looks certain to shatter his previous best of 4.6million pay-per-view purchases. We're going to do UFC Embedded like we do for our fights, and a couple of other things.
Mayweather didn't become one of the best boxers in the history of the sport by overlooking opponents and he won't start with McGregor.
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"I'm a realist", Leonard Ellerbe, chief executive officer for Mayweather Promotions, said during a conference call Wednesday night. We'll just have to wait and see if that's even close to enough to compete with one of the greatest boxers of all-time. Conor McGregor is 27 and he is a southpaw. The two men will meet at the light-middleweight limit of 154 pounds, which bodes well for McGregor, who is now the UFC's 155-pound champion.
"As with every Mayweather and McGregor fight part of the appeal is the spectacle and outsize personalities who are participating in it", Espinoza said.
Rumors and reports of a fight have been floating for nearly a year, with both fighters openly acknowledging a potential bout.
"As we've already seen this evening, Mayweather vs. McGregor has generated buzz that reaches far beyond that of the considerable boxing and MMA audience".
"McGregor has a lot of confidence because of what he's achieved in the UFC but he's not getting in there with a domestic-level fighter, he's getting in there with one of the greatest fighters of all time".
It's being speculated that both men will be paid a staggering $100 million each for the fight to be aired on pay-per-view TV.