Charlie Hunnam will play Arthur, with Astrid Berges-Frisbey playing Guinevere. Jude Law is also in talks for the role of the villain.
Ritchie will direct with a script from Joby Harold. Ritchie and Harold are also producing along with Lionel Wigram, Akiva Goldsman and Tory Tunnell.
Plot details are being kept under wraps, though the pic is set to open on July 22, 2016. Niija Kuykendall and Cate Adams are overseeing for the studio.
The studio hopes the film can kick-start another franchise for Warner Bros., with the story to be told over six installments.
For Bana, the role isn’t the biggest, but the studio and Ritchie were always looking for a big name for the part to make a splash for the time he is onscreen, originally going to Liam Neeson before circling back with Bana.
Bana, who is repped by WME, recently wrapped production on Disney’s “The Finest Hours” and is also attached to star in the spy action comedy “Special Correspondents,” which has Ricky Gervais writing and directing as well as Jim Sheridan’s “The Secret Scripture.”