The information was confirmed by the author of the successful saga, E L James, in person, on her Twitter page.
“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,” she wrote.
Not long after that, James also revealed the name of the male protagonist.
“The gorgeous and talented Charlie Hunnam will be Christian Grey in the film adaptation of Fifty Shades of Grey,” she Tweeted Monday.
Daughter of Melanie Griffith and Don Johnson, 23-year-old Dakota is known for her roles in The Social Network, Need for Speed, 21 Jump Street and television in Ben & Kate.
Hunnam, 33, was the hero of the TV series Sons of Anarchy, and he also starred in the blockbuster Pacific Rim.
The film will be released on August 1 next year and will be directed by Sam Taylor-Johnson.