Author E.L. James announced the big news on Monday (02Sep13), revealing The Social Network star, whose father is Miami Vice veteran Don Johnson, had been chosen to portray adventurous college student Anastasia Steele on the big screen.
Taking to her Twitter.com blog, James wrote, "I am delighted to let you know that the lovely Dakota Johnson has agreed to be our Anastasia in the film adaptation of Fifty Shades of Grey."
Minutes later, she added, "The gorgeous and talented Charlie Hunnam will be Christian Grey in the film adaptation of Fifty Shades of Grey."
Johnson's casting comes just days after she was tipped for the role, ahead of the likes of Emma Watson, Kate Beckinsale and Alexis Bledel, while Sons of Anarchy star Hunnam also recently emerged as the hot favourite to play masochistic billionaire Grey.
British filmmaker Sam Taylor-Johnson will direct the movie.