Brody Jenner's ass was tapped to perform at the biggest porn event of the year -- he'll be getting handsy at the opening party for the sex industry's Oscars ... as the house DJ.

Our impeccable porn sources tell us the Adult Video News Awards Show (AVNs) lined up BJ and DJ William Lifestyle to double team the Kickoff Party on Jan. 21st at the Hard Rock.

As we first told you ... the AVNs are also gunning for Lorde to perform during the award ceremony. No word if she's officially turned them down responded yet.

We're told Brody's pulling in five figures for the gig ... plus fringe benefits, of course.