The actress, currently appearing in Line of Duty, Hawes will play Ms Delphox, a powerful out-of-this-world character with a dark secret.
She’ll appear opposite new Doctor Peter Capaldi and companion, Clara Oswald (Jenna Coleman) who’ll encounter the mysterious Ms Delphox when they arrive on a strange and puzzling planet.
Written by Steve Thompson (Sherlock) the episode will be directed by Douglas Mackinnon (Line Of Duty, Doctor Who).
Commenting on her role, Keeley Hawes, said: “I am delighted to join Doctor Who and to be working with this incredible team. Ms Delphox is a great character and someone I’ve had a lot of fun playing.”
Lead writer and executive producer, Steven Moffat, added: “Anyone watching Jed Mercurio’s amazing Line Of Duty will know that Keeley Hawes is having one hell of year. And now it’s about to get even better as she achieves the greatest villainy yet attempted on Doctor Who: she plays a banker.”