Turn Left

"Turn Left" is the eleventh episode of the fourth series of British science fiction television series Doctor Who. It was written by showrunner Russell T Davies and broadcast on BBC One on 21 June 2008.

David Tennant only makes a small contribution to this "Doctor-lite" episode as the Tenth Doctor. The story instead focuses on the Doctor's companion, Donna Noble (Catherine Tate) and her encounters with former companion Rose Tyler (Billie Piper). The episode's narrative focuses on an alternative history where the Doctor dies during the events of the 2006 Christmas special "The Runaway Bride". The episode depicts a dystopia caused by the Doctor's death, leaving Rose to convince Donna to save the world. The beginning and end of the episode take place in the show's normal continuity, and the end features a cliffhanger that leads directly into the series finale "The Stolen Earth".

Davies' writing and Tate's performance were acclaimed, and the episode was praised for its depiction of dystopia in a scene characterised by the internment of a foreign citizen. The episode was the fourth-most-watched programme in the week it was broadcast, with 8.1 million viewers, and the Appreciation Index of the episode was 88, considered excellent. The episode was one of two Doctor Who stories in the fourth series to be nominated for a Hugo Award in the Best Dramatic Presentation, Short Form category.