The date for the most ludicrous professional bout since Rocky Balboa took on wrestling champion "Thunderlips" in Rocky III has been set.
In March, Mayweather announced that he was coming out of retirement specifically to fight McGregor.
The 40-year-old Mayweather, who retired with an undefeated 49-0 record in 2015, made the announcement on Instagram Wednesday.
McGregor will be the overwhelming underdog, but win or lose the showdown is likely to propel him into the consciousness of many non-fight fans around the world.
Mayweather is one of the best pay-per-view draws the sport has ever seen as Forbes listed him as the highest-paid athlete in the world in 2014 and again in 2015.
The pair first mooted the idea of a fight in a series of exchanges on social media, in which the Irishman urged Mayweather to step up and sign.More news: Qatar Airways seeks 10% stake in American
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In the United States, Showtime will cover the pay-per-view which will nearly certainly break records given the drawing power of both men involved.
Neither Mayweather or McGregor have competed this year. He's boxing against Mayweather, who's 49-0 in his boxing career.
"(McGregor) is absolutely 100 per cent positive that he wins this fight, and I stopped doubting Conor McGregor a long time ago", he insisted.
The pay packet for each fighter is around $100 million Dollars. The biggest question left to answer: will people actually tune in to watch McGregor and Mayweather go at it?
The mixed martial arts fighter McGregor is already a heavy underdog in the fight.