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.