He’s been working to bulk up for a new film role, and Robert Pattinson headed over to a fitness center in Los Angeles on Sunday (September 22) with an unidentified brunette beauty.

The “Twilight” hunk tried to go unnoticed in a black hooded sweatshirt, and insiders have reported that he’s spent a ton of time at the gym with his mystery woman.

Over the weekend, Rob brought his new gal to a birthday party for Shoshana Bush and they were all about public displays of affection.

An eyewitness told Radar, “Rob and the brunette turned up around midnight. They were cute together. At one point, he was talking to someone and she wandered over and grabbed his hand and pulled him to over to near the pool. Their hands were all over each other!”

Another source added, “She's really sweet and girl next door vibe. Rob is actually really nice and humble. They're a perfect match!”