This weekend finally sees McGregor and Mayweather enter the ring to see if an MMA fighter can do the impossible and beat the undefeated boxing champ.
It's been billed as the biggest sporting event in history and will see both competitors walk away with over 100 million dollars each, and neither man is shy when sharing the fruits of their labour, at least on Instagram any.
We've taken a look at both fighters top ten cars to see who wins the car collection crown!
1 Rolls Royce Wraith
Unsurprisngly the British luxury brand features heavily in both lists, they've been making cars for the rich and famous for a over a hundred years after all. This is one of their fastest though and despite its boxy frame can do 0-60 in 4.4 seconds!
2 Bugatti Veyron
This car needs little introduction, the fastest street legal production car in the world, it's the top trump.
3 Rolls Royce Drop Head
Not one for your shrinking violets out there, nothing says look at me like a convertible with more decking than my back garden.
4 A pair of Ferraris
This Italian couple cost a cool £200k each, quite modest compared to some of the other cars on this list though.
5 Lamborghini Aventador and Mercedes SLS
Nothing says supercar like a Lambo and the Aventador is a proper kid's dream car. The Mercedes on the other hand is a petrol head's machine, Lewis Hamilton and Jeremy Clarkson have both owned one.
6 More Bugattis and a Private Jet
Three of the fastest cars in the world and your own airplane, bit better than my profle pic.
7 Ferrari Enzo
No collection is complete without a red Ferrari, the Enzo is named after the company's founder and is no slouch reaching 100mph in 6.6 seconds!
8 Koenisegg Trevita
The most expensive car on this page by quite some way, $4.8m is a lot to pay for what was a six year old car at the time although most of these motors appreciate in value. I wonder how many miles were on the clock?
9 Rolls Royce Phantom Limo
Favourite of British boxing champs, rumour has it Anthony Joshua has his eye on one of these, this car completes Mayweather's blinging fleet of rollers.
10 Bentley Golf Cart
Not strictly a car but this is too cool to leave out, Floyd Mayweather had this Bentley golf cart custom built for his son's birthday!
1 Lamborghini Aventador
Not a bad place to start, although apparently this Lambo got towed recently when McGregor left it parked in Dublin on double yellow lines!
2 Rolls Royce Wraith
McGregor felt the wrath of this Wraith's owner recently when he got threatened with legal action for standing on the motor, which was just on loan from a Merseyside luxury car dealer.
3 Range Rover Fleet
Not quite as expensive as some of the other cars on here but then there does seem to be a fair few Range Rovers in this picture!
4 Rolls Royce Drop Top Dawn
RR call it the sexiest car they've ever built, it's said to be inspired by the movie La Dolce Vita and certainly looks sweet to us!
5 Cadillac Escalade
Conor McGregor seems to have a habit of naming his cars, this is the Franklin. With over 100 vehicles I think Mayweather has probably got too many to give them all their own monikers!
6 McLaren 12C
McGregor recently got pulled over by the cops driving this in Dublin, it's certainly got the looks to stop traffic.
7 Lamborghini Huracan Avio
Apparently Conor McGregor plans to start importing super cars to Ireland, if he keeps buying green ones like this Lambo I'm sure they'll sell well.
8 BMW i8
Proving his green credentials McGregor owns a fully electric i8. This BMW is proof, if it were needed, that you don't need a petrol engine to make an amazing sports car!
9 Volkswagen Amarok
He's clearly got good taste in pickups with this VW, you can read our review of the beast here.
10 Golf cart
Not quite a Bentley golf cart but nice try anyway Conor...