"Deep Breath" is the first episode of the eighth series of the British science fiction television programme Doctor Who, first broadcast on BBC One and released in cinemas on 23 August 2014. It was written by showrunner and executive producer Steven Moffat and directed by Ben Wheatley.

In the episode, the newly regenerated Twelfth Doctor (Peter Capaldi), and Clara (Jenna Coleman) land in Victorian London where they find a dinosaur rampant in the Thames and a spate of deadly spontaneous combustions. However, their friendship is put in jeopardy as Clara struggles to cope with the Doctor's new incarnation.

The episode has the first full-length appearance of Peter Capaldi as the Doctor, with Coleman reprising her role as his companion Clara from the last series. It also features Neve McIntosh, Catrin Stewart, and Dan Starkey reprising their roles as Madame Vastra, Jenny Flint, and Strax, as well as Capaldi's predecessor, Matt Smith, in a cameo appearance. The episode sets up the main story arc of the series revolving around a mysterious woman called Missy (portrayed by Michelle Gomez), who is often seen welcoming people who have died throughout the series to the "Promised Land", a place that serves as an apparent afterlife to deceased characters.

Deep Breath was watched by 9.17 million viewers, the highest ratings for a premiere since Matt Smith's first episode as the Doctor in 2010 and received positive reviews, with many critics praising the performances of Capaldi and Coleman, Moffat's script, and the introduction and stylisation of the new Doctor, though Smith's cameo received mixed reviews.