Steven Tyler's Interested in Floyd Mayweather's Million Dollar Bugatti

Floyd Mayweather's Bugatti may get a new celebrity butt in the driver's seat cause Steven Tyler is seriously interested in buying the champ's insanely expensive whip.

TMZ Sports spoke with RD Whittington -- co-owner of Luxury Auto Collection in Scottsdale, AZ -- who says he scored the listing for both of Floyd's Bugattis and plans to unload his white 2011 Veyron Grand Sport at the Barrett-Jackson auto show this weekend.

Floyd reportedly paid $3.5 million for the car ... and it's expected to fetch EVEN MORE at auction.

Whittington tells us the car is getting serious interest from car enthusiasts including Tyler who happens to be selling his million dollar Hennessey Venom GT Spyder for charity at the same auction.

We're told after Tyler unloads his car, he's already talking about swooping in on Floyd's ride.

If you still want a Mayweather supercar, his black 2015 Veyron Grand Sport Vitesse is also for sale at the L.A.C. shop for $4.95 million.

So, why's Floyd getting rid of these beauties? Get this ... we're told his new obsession is JETS.