Access Hollywood has learned that Guy Ritchie has cast Rachel McAdams in the main female role for his version of Arthur Conan Doyle’s world of Sherlock Holmes.

For Sherlock Holmes, McAdams will be joining a great cast including Robert Downey Jr. as Holmes, Jude Law as Watson, and Mark Strong (Stardust, Syriana) as Lord Blackwood.

Though Access Hollywood didn’t give a specific character, it’s assumed that McAdams will be playing Mrs. Irene Adler, the most popular female character in the Holmes universe, in part to her outwitting the clever detective.

Joel Silver and Downey Jr.’s wife Susan Downey are producing and the movie is looking to come out some time in 2010.