Mel Gibson Is Single Despite Rome PDA Pics, Back in U.S. With 'Passion 2' Wrapped

Mel Gibson was snapped in the middle of some PDA with a babe in Rome ... but TMZ has learned he's back in the U.S. -- and very single -- having just wrapped on a massive project.

Here's the deal ... the actor-director star and the Italian celeb Antonella Salvucci were snapped smooching in Rome ... which, of course, led fans to ask "What's going on, Romeo?"

Sources with knowledge tell TMZ ... the pictures were of Mel saying goodbye to a good friend ... he's single and has been back in the U.S. for about a month, having just wrapped "The Resurrection of the Christ: Part One" -- the follow-up to his 2004 blockbuster "The Passion of the Christ."

As we reported ... Mel and longtime partner Rosalind Ross separated last year ... after nine years and one child together. And those pics with Antonella were the first of Mel and a possible new squeeze -- so, a big deal.