I think there are many actresses that could play [The Doctor] because there are so many wonderful actresses. I mean, it would change the role because she would be a woman so when you put her in a room full of men, it’s a different scenario than if you put a man in a room full of men, because she’s a different sex. Would it change the fundamentals of the character? No. But it’s an interesting idea, if the Doctor’s a woman, does she have a Doctor baby? Is there a mini-Doctor? I don’t know, who knows? What actresses could play her? Oh gosh, so many, so many could play her. It depends on what age you would want…. It could be…Charlize Theron is pretty kick ass, isn’t she? They just have to find a brilliant actress.

Matt Smith answers the question “Is there an actress you could see playing the Doctor, and how do you think that would change the role?” The Mary Sue

Also: if you’ve seen the misquote that Matt Smith supposedly says that there will never be a female Doctor, here’s what he actually said:

Matt: I never see that happening any time soon to be honest. I don’t think it will happen.

The Mary Sue: Because you’re not leaving us?

Matt: No. (because he’s not leaving us) And I’m not turning into a woman.