Rob Gronkowski -- Hey, Mr. Kraft ... I've Got a Classy Side, Too!

Rob Gronkowski isn't just about party buses and booze cruises, he can class it up sometimes ... but with a touch of Gronk thrown it in.

The New England Patriots stud recently picked himself up a new Mercedes AMG S63 from Bernie Moreno and the folks at Mercedes Benz of Berlington, MA.

Moreno tells TMZ Sports dealing with Gronk was a breeze, saying, "He’s the absolute real deal. What you see is what you get. A really nice guy who loves what he does and is as genuine as I have ever met."

As for the actual car, Moreno says it was "fully-loaded" with 577hp, rear seat entertainment system and -- in a feature that sounds like it was created specifically for Gronk -- the car comes with a small fridge in the back.

Gronk gonna Gronk.