British actress Sienna Miller (Factory Girl, Stardust) will play The Baroness in Stephen Sommers' live action depiction of G.I. Joe. According to Variety, she will play "the film's female lead, described as a raven-haired baroness and sexy femme fatale skilled in espionage." I'll confess that I didn't watch a lot of GI Joe as a kid, but isn't The Baroness a member of the evil COBRA Organization? So when Variety says "female lead" they must not mean she'll be the protagonist; they probably just mean, "only woman." So far, Miller is the only actor officially cast. Producer Lorenzo di Bonaventura must have liked what he saw of her in Stardust.
Paramount has set a February start date, though the strike could put that in jeopardy, along with everything else. Currently the release date is slated for August 7, 2009.
-David Morgan
Updated by Senior Editor F.F.F.!
Here is Sienna Miller:

Here is The Baroness:

Here is a good casting choice for The Baroness courtesy of Umbrax:

Here is a random hot chick in cosplay as The Baroness:

Everything you ever wanted to know about The Baroness can be found here.
Finally, here is Olivia Munn as The Baroness:
Sienna Miller is not The Baroness. I hate to say she isn't nearly as hot as the character is made out to be, plus can she actually pull of a Hungarian/Russian/Bulgarian/Whatever it is/ accent?
Comments
This is the trailer to a live action GI JOE movie!!!!! This one has a great Baroness. This is for real folks. Just look at the first 1 second and you'll know that this is the real deal.
You must see this folks.