She is 23. She is a movie star. She is a millionaire. And she is famous around the world, a best-actress Oscar nominee (one of the youngest), a fashion icon (the subject of a current, extensive spread in Vogue) and a sex symbol (recently voted, in one poll, as the woman with Britain's most seductive voice).

And yet, Keira Knightley is not without regrets. "The only thing I do wish is that I'd changed my name," she says. "As an actor, what I look like, my face, is used all the time for different characters, so I'm sort of used to that."

But what really disturbs her, she says, "is when I see my name in those stories, because I can't disassociate myself from that. It's like 'The Crucible,' when they're trying to get him to sign the confession and he won't. I used to think 'How stupid, just sign, what does it matter?' But your name should belong to you."

And, over a very brief and amazing career, Knightley has made hers known.

It would have been enough to just be the teen star of "Bend It Like Beckham." It would have been more than enough to just be the action-film femme of the three "Pirates of the Caribbean" hits. But then Knightley added "Pride and Prejudice" to that, and won an Oscar nomination. And then tacked on "Atonement."

And now the opulent, tragic biography "The Duchess."

The story of Georgiana, the 18th-century Duchess of Devonshire -- and ancestor of Princess Diana -- it's the familiar story of a colder, older husband, a naively romantic bride and a marriage marred by dishonesty, infidelity and the all-important need for a male heir. The parallels are evident (and, in fact, the movie's poster even rewrites a line of Diana's -- "There were three people in her marriage").

But Knightley is an actress, not an essayist. The parallels don't interest her. It's the character that fascinates.

"Georgiana had this huge public profile and yet she was intensely lonely in her private life," Knightley says. "Wanted to have everybody looking at her -- and yet she had no self-esteem. Always doing the one thing that is absolutely going to hurt her -- and yet she's a survivor ... Contradictory and interesting and incredibly tragic. I adored the whole arc of the person -- but, oh, now I'm sounding terribly pretentious," she said with a laugh.

"One of the things I love about period films is that they're so removed from your own reality," she continued. "It's exactly what acting's about for me, diving into this complete fantasy. I think that's why I like watching period films, as well, because it's a complete removal from today, and your imagination is given free rein."

Knightley scored successes in "Pride and Prejudice" and "Atonement" -- the latter inching her, at least, into the first half of the 20th century. But while the actress jokes about longing for a role that allows her to act in jeans and a T-shirt, she admits her period clothes also function as a kind of armor.

"Definitely, absolutely, without a shadow of a doubt it's hard for me to play someone too close to who I really am," she says. "I think that's why I'm at my absolute happiest once you give me an accent, or a wig.

"But, you know -- and it's a huge generalization -- I think that might be the difference between English actors and American ones. Americans are very good at playing parts close to home, honing down their own personas and then playing off that. I think we're much more comfortable distancing ourselves from our roles."