The 2 were having a blast Monday night at the world premiere of Ben's new movie, "Air" ... and, of course, the couple was holding court on their way into L.A.'s Regency Village Theater.

They even gave fans what they came for ... sharing a few kisses and chattin' it up with the photogs snapping pics. They might have been acting like they were the only 2 there, but they weren't -- Ben's costars Jason Bateman and Viola Davis were also there to kick off the film.

J Lo and her man were still giving honeymoon vibes at the after-party where they cozied up on a couch. You can see the meme now, can't ya? "Find someone who looks at you the way Ben looks at Jen."

Ben also delivered a speech at Monday night's event ... giving his buddy and costar Matt Damon top billing as he called him the "biggest joy of my professional life."

Don't worry his wife got some attention too, telling her, "You’re fabulous, you’re amazing, you’re wonderful, good, kind, magnificent and I love you.”

Ben directed "Air," and produced it with Matt ... the movie's about the Nike sales team's efforts to strike a deal with an NBA rookie named Michael Jordan.