"I didn't feel like I deserved to play her," said former Home and Away actress.
"I didn't go to drama school. I didn't go to university. I had it in my head that in order to play such a prominent historical character, I should be well-versed in this world," she said.
With iconic portrayals of the role by Cate Blanchett, Katherine Hepburn and Judi Dench, Robbie admitted she was nervous she wouldn't live up to peoples expectations.
"I was like, 'I don't belong in that group'. They're insane. They're so good," she said.
Margot's interview comes two weeks after she confirmed she will be starring as Barbie in the upcoming live-action film.
"Playing with Barbie promotes confidence, curiosity and communication throughout a child's journey to self-discovery," Robbie dished, explaining that the film aims to inspire young girls. "I'm so honoured to take on this role and produce a film that I believe will have a tremendously positive impact on children and audiences worldwide," she continued.
Robbie's co-stars are yet to be announced.