Rob Gronkowski -- I'm Gonna Be in the 'Entourage' Flick

NFL star Rob Gronkowski is goin' Hollywood ... TMZ has learned Gronk is about to become a real-life movie star ... 'cause dude just signed on to a monster Hollywood film.

We got word from Gronkowski's theatrical manager Henry Penzi ... the NE Patriots' stud is going to be hugging it out with Jeremy Piven, Adrian Grenier and the rest of the boys from "Entourage" in their upcoming feature film.

The movie starts shooting in January ... we're told Gronkowski won't have to stretch his acting abilities too far ... 'cause he's going to play himself (spoiler?)

So far ... no word on what kind of scene he'll shoot ... but given his history ... we wouldn't be surprised to see Gronk partying it up with a bunch of hot babes.