James, who currently appears on PBS's "Downton Abbey," made her feature debut in 2012's "Wrath of the Titans." She'll star in "Cinderella" alongside Cate Blanchett, who plays the evil stepmother in the Kenneth Branagh-directed production.
Rumors about who would land the coveted leading role had been swirling for months, with Emma Watson reportedly turning down the part. The search was recently said to have been narrowed down to a choice between James, Bella Heathcote ("Dark Shadows"), and Margot Robbie ("Pan Am").
Now that Branagh has his princess, he still needs to find a prince, though "Game of Thrones" star Richard Madden has apparently caught Disney's eye. The studio is aiming to release "Cinderella" sometime in 2014.