Floyd Mayweather -- Drops $300K On Land Yacht ... With 55 Inch TV, Bar & Massage Chairs!!

Floyd Mayweather dropped $300,000 on an insanely luxurious customized Mercedes party bus ... with a HUGE TV and BAR ... and had it shipped across the desert last night ... TMZ Sports has learned.

The whip ... a souped up Mercedes-Benz Sprinter a.k.a. "Land Yacht" ... was designed specifically for Floyd ... and it's AMAZING ... even for a guy with an RIDICULOUS car collection worth over $7 mil!

The specs ... 55 in. TV with Apple and DirecTV, Surround Sound stereo system, Maybach heated massage chairs, Champagne bar, and cabin lighting system ... to name a few.

Our sources tell us Floyd wanted the party bus last night ... so Fusion Luxury Motors in L.A. ... who acquired the Land Yacht for the champ ... delivered it from Cali to the boxers Vegas mansion.