The 25-year-old Australian actress revealed she's a huge fan of the series on Tuesday's episode of Jimmy Kimmel Live! after Kimmel shared a childhood photo of her reading Harry Potter and the Order of the Phoenix.
"Literally the most embarrassing photo of my whole life," Robbie said of the picture. "I actually think that was on my 13th birthday."
"I'm drinking a cup of tea. I'm in bed. I'm clearly really enjoying myself reading Harry Potter. I have braces, which I had for two years. I was really into slicking my hair back -- God knows why," she recalled.
"I am wearing glasses, which I actually didn't need. I have 20/20 vision and I lied to get glasses so I could look like Harry Potter," the star admitted. "They're not even cool ones, they're, like, ugly glasses."
Robbie will next star in The Legend of Tarzan, which is directed by Harry Potter helmer David Yates. The actress will play a strong and independent version of Tarzan's (Alexander Skarsgard) wife, Jane Porter, in the film.
"It was very important that we didn't want it to feel archaic or dated, where it's like, tough guy has to save the poor girl," Yates previously told Entertainment Tonight.
"If you enter the jungle with anybody, you want to go with Margot Robbie. She's practical, and she's smart, and she's resourceful. And she can take care of herself," the director lauded.