Keira Knightley feels she owes Anne Hathaway an apology after she was "rude" to a fan who mistook the British actress for the Les Miserables star.

The Pirates of the Caribbean beauty was spotted at an airport on her way to the Toronto International Film Festival in Canada back in September (14), when she was approached by a fan and asked to pose for a picture.

However, Knightley refused after realising the devotee had gotten her celebrities mixed up.

She tells Australia's Daily Telegraph, "At the airport, a woman mistook me for Anne Hathaway.

"I think I have to apologise to Anne Hathaway because the woman (at the airport) thought I was being really rude as Anne Hathaway, not giving her a picture as Anne Hathaway, but I was really only saying that I promised I wasn't Anne Hathaway, which I am not."

And Knightley admits it's not the first time she has been mistaken for fellow actresses.

She adds, "Actually, it's the first Anne Hathaway I have had. Generally, I get a lot of Rachel Weisz and Natalie Portman."