Lily James decorated her bedroom with pictures of Ryan Phillippe when she was a teenager.
The 'Pride and Prejudice and Zombies' actress - who is in a relationship with Matt Smith - had a huge crush on the 'Cruel Intentions' star and "really loved" him.
She said: "My first movie crush was Ryan Phillippe. He covered my bedroom walls.
"I didn't have proper posters of him, I made collages using Microsoft Word - an A4 sheet that was 15 tiny pictures of Ryan Phillippe. I really loved him."
The 26-year-old star was a presenter at the recent Golden Globe awards and shared a "surreal" moment backstage with Lady Gaga.
Asked when she last got starstruck, she said: "I had a little moment with Lady Gaga [at the Globes].
"We were backstage because I was presenting and she held on to me at one point, which was amazing.
"She held my shoulders. I just smiled. It was very surreal."
Though she was invited to the prestigious awards ceremony, Lily doesn't feel particularly famous.
Ranking her fame on a scale of one to 10, she told Empire magazine: "Four? I sometimes do ridiculously crazy things.
"I went to the Golden Globes but I don't really feel I'm at Globes level."