Astrid Berges-Frisbey (I Origins) has signed on to star in Warner Bros.' Knights of the Roundtable: King Arthur as Guinevere. The actress beat out a number of notable actresses who were vying for the role, including Elizabeth Olsen, Felicity Jones and Alicia Vikander.

Sons of Anarchy star Charlie Hunnam signed on last month to play the title character, with Idris Elba joining the cast in July as Bedivere, the right-hand man to Arthur's father who teaches the young Knight how to fight. In the classic King Arthur tales, Guinevere is Arthur's lover before she betrays him for Lancelot, although it isn't known if that story line will be used here.

No specific story details have been given, but we reported in January that Warner Bros. is eyeing a six-movie franchise that will be spawned from this project. Joby Harold (Edge of Tomorrow) wrote the screenplay, which is expected to focus on the title character's early years.

RELATED: King Arthur Trailer #3 Explores the Legend of the Sword

Guy Ritchie is directing, with Akiva Goldsman and Tory Tunnell producing. It isn't known when production will get under way.

Astrid Berges-Frisbey is best known for playing the mermaid Syena in 2011's Pirates of the Caribbean: On Stranger Tides, and she also starred in The Sex of the Angels.