Robert Pattinson says Kristen Stewart is the only person who can understand him.

The 26-year-old actor has been dating his Twilight Saga co-star for around three years and admits she's perfect for him because she knows what he's going through.

"She understands exactly how I feel. She is an ambitious woman who wants to grow as an actress. She has an excellent radar for what is good and challenges me constantly," he said.

Robert also said it was nice to go to the Cannes Film Festival with 22-year-old Kristen because they could both support each other: "In the end, it was amazing to have each other's support. Her presence at the gala screening of Cosmopolis made me really nervous. She was sitting in front of me. I kept looking at the back of her neck, trying to find out if she was liking the movie or not. I only calmed down when, at the end, Kristen told me she loved it."