Credit:; Fame Pictures

Blame it on Rio!

Rob Pattinson and Kristen Stewart had a serious makeout session in Rio de Janeiro, Brazil on Saturday -- shooting scenes for Breaking Dawn, of course.

Pattinson, 24, and Stewart, 20, haven't been photographed together in a while, but have reunited to shoot the fourth and fifth installments of the Twilight franchise (the epic fourth book in the series has been split into two films). See more shots of Robsten in Brazil!

While most of the flicks will be shot in Baton Rouge, La. over the next eight months, the Twilight crew hit Brazil to shoot the honeymoon scenes after their characters tie the knot.

The duo were photographed a month ago in L.A. -- where they had an affectionate night out. After an intimate meal at eatery Ago, they stopped by Soho house, where Stewart was "sitting in his lap," according to an eyewitness. "It was a snugglefest!" the observer adds of their "cute PDA."