The legendary DJ recently had his Ford Super Duty COMPLETELY redone by some of the best in the biz -- RDB LA -- and his new whip's an absolute beast. The ride is a whopping 26-feet long with 2 extra wheels for a 6x6 conversion -- 4x4s are for losers -- and a TRAIN HORN. Move bitch, get out the way!!!

The interior is giving us all the EDM feels ... with Marshmello opting for a Rolls-Royce Starlight Ceiling with 20 types of LED lights to keep the party going. In a super baller move, he got his name engraved in the headrests.

Everyone's gonna know who's behind the wheel ... the truck is covered in Marshmello logos on the doors and bumper. And, we gotta say, we're feeling the custom body flares and matte green wrap.

Marshmello hit up Mano and Vik at RDB LA for the custom job -- the music icon and his manager, Moe Shalizi, go way back with the shop owners and trust their work -- and the entire remodel took months to complete and cost $500,000!!!

As you can see ... it's a major upgrade from the Ford's $35k to $50k stock price.