OK! EXCLUSIVE: Ryan Gosling & Michelle Williams are Real-Life Valentines

Co-stars Ryan Gosling and Michelle Williams share some steamy scenes in Blue Valentine — and apparently it's no acting stretch!

OK! HOT GALLERY: RYAN GOSLING MAKES FANS SMILE AT SUNDANCE

"They're dating," a source confirms to OK!. The pair stepped out at last month's Sundance Film Festival, in Utah, where their flick won raves.

OK! HOT GALLERY: MICHELLE AND MATILDA DOLL UP BROOKLYN

The once Oscar nominees, both 29, "respect their private lives and don't want to go public," the source says. "But they've been seeing each other for a few months."