After a few months of negotiations, it was made official and it was set to take place at the T-Mobile Arena in Paradise, Nevada on August 26, 2017.
It was also confirmed that Mayweather and McGregor would take part in a four-day worldwide press tour in July. Billed as the 'MayMac World Tour', the fighters stopped off in Los Angeles, Toronto, Brooklyn and London.
The final leg of the tour was at London's Wembley Arena. These four days provided huge entertainment and it did wonders to promote the fight.
This almighty clash stood to be the most lucrative in the history of the sport. Mayweather was coming out of it the better, as he was guaranteed to make $100million just for stepping into the ring.
McGregor meanwhile was set to make at least $30million, but this was expected to rise to over $100million once his additional income was taken into account.
A fight of this magnitude needed a stacked undercard, and that was what fans got. Gervonta Davis beat Francisco Fonseca via an eighth-round KO in the chief support. This saw him win the vacant IBF world super featherweight title.
Elsewhere on the card, Badou Jack defeated Nathan Cleverly via TKO to become the new WBA world light heavyweight champion. Savannah Marshall also made her professional debut during the unaired prelims.
How the fight unfolded...
In the end, these paled into insignificance when it came to the main event. McGregor was around 20 pounds heavier than "Money" in the ring.
This helped to begin with as the UFC superstar made a promising start, as he was ahead on the cards after the first few rounds.
Mayweather stuck to the tactics that he had mastered over the years to avoid any big hits from his opponent. He even pulled out the famous rope-a-dope technique, that had been used brilliantly by Muhammad Ali in 1974 against George Foreman in the Rumble in the Jungle.
'Pretty Boy' made a cautious start, which allowed McGregor to have some joy in the early going. This made some onlookers start to truly believe that the Irishman could pull off a massive shock to hand Mayweather his first professional loss.
A big concern for McGregor fans heading into the fight was his fitness levels in a boxing ring. He comes from a UFC background and they fight for a maximum of 25-minutes, which includes five rounds.
He was now having his first-ever professional boxing match over 12 three-minute rounds. Add this to the fact that he was against Mayweather, one of the greatest of all time, and you see that the obstacles start to line up against McGregor.
This proved to be true on the night as the UFC fighter started slowing in the middle rounds. In turn, this encouraged Mayweather to come forward far more than he had done in the early going.
'Money' stepped it up a gear in the ninth round, as he landed a flurry of punches to the head of McGregor. His dominance continued into the tenth until the referee waved the fight off with 1:55 left of the round.
The bout proved to be more interesting than some expected, and it also delivered when it came to the revenue.
The Nevada State Athletic Commission (NSAC) revealed that the live gate surpassed $55,000,000 on the night. It was later reported that Mayweather-McGregor generated around 4.4 million buys in the states, which is just less than the 4.6 million for Mayweather-Pacquiao in 2015.
With everything included, Mayweather earned roughly $280million, while McGregor took away around $130million.
What have Mayweather and McGregor done since?
This win took Mayweather's record to 50-0 (27KOs), but he has not fought professionally since. Instead, the 44-year-old has started to take exhibition bouts.
His one fight so far came against Japanese kickboxer Tenshin Nasukawa on December 31, 2018. Mayweather won via TKO in the opening round and he has recently been linked with bouts against YouTube stars Logan Paul and Jake Paul.
Since his loss to Mayweather, McGregor has had three more UFC fights. He fought Khabib Nurmagomedov in 2018 in a tense clash for the UFC lightweight championship.
Khabib submitted the Irishman in the fourth round, which led to him taking over a year out of the Octagon. He made his return in January 2020, as he knocked out Donald Cerrone in the opening minute at UFC 246.
'Notorious' took another year out before his clash in January 2021 against Dustin Poirier. This was a rematch from McGregor's win in 2014. Poirier got revenge this time as he got the victory via TKO in the second round.