Knightley will be playing alongside Chris Pine, who will be playing Jack Ryan, and Kenneth Branagh, who will be playing the villain as well as sitting in the director's chair.
The script was written by Mission: Impossible writer David Koepp, and follows the story of a young Jack Ryan working in Moscow. He comes across plans to render the US Dollar worthless, and works to thwart them.
Production on the film begins next month.
