The ninth series of the British science fiction television programme Doctor Who premiered on 19 September 2015 with "The Magician's Apprentice" and concluded on 5 December 2015 with "Hell Bent".

The series' main story arc revolves around the mystery of a being called the Hybrid, the combination of two great warrior races.

The other writers who worked on this series included Toby Whithouse, Jamie Mathieson, Catherine Tregenna, Peter Harness, Mark Gatiss, and Sarah Dollard.

In Doctor Who Magazine, Michelle Gomez confirmed that she would return as Missy, the latest incarnation of the Master, who served as the main villain in series 8.

[16] It was later announced that other guest actors featuring in the first block would include Arsher Ali, Morven Christie, Neil Fingleton, Colin McFarlane, and Steven Robertson.

[20] On 5 August 2015, it was announced that Reece Shearsmith, Elaine Tan, Neet Mohan, Bethany Black and Paul Courtenay Hyu would have a role in "Sleep No More".

[21] Other guests included India Ria Amarteifio, Dasharn Anderson, Harki Bhambra, Daniel Hoffmann-Gill, Aaron Neil, Demi Papaminas, Joey Price and Jami Reid-Quarrell.

[19] On 30 March 2015, Maisie Williams, Rufus Hound, Tom Stourton, Ariyon Bakare, Simon Lipkin, Ian Conningham, Murray McArthur, Barnaby Kay, John Voce, and Struan Rodger were announced to be appearing.

[26] On 28 September 2015, it was announced that Corey Taylor, frontman for the heavy metal band Slipknot, would feature in the fourth episode "Before the Flood", as the scream of the alien warlord Fisher King,[27] whose voice was provided by Peter Serafinowicz and whose body was portrayed by Neil Fingleton.

[32] As the series coincides with the 10th anniversary of the show's revival, the BBC asked former showrunner and head writer Russell T. Davies to return, but he declined.

[40] On 30 March 2015, it was confirmed Jamie Mathieson, who previously wrote "Mummy on the Orient Express" and "Flatline" for series 8, would write a new episode called "The Girl Who Died" with Moffat.

Filming and principal photography for the ninth series began on 5 January 2015 in Cardiff,[44] with "Under the Lake" and "Before the Flood" making up the first production block.

[48] On 30 March 2015, it was announced that Ed Bazalgette would direct two episodes, one written by Jamie Mathieson and Steven Moffat and the other by Catherine Tregenna.

[22] On 8 May 2015, the BBC announced that filming had started on a two-part episode written by Peter Harness and directed by Daniel Nettheim.

[20] On 10 June 2015, it was revealed by the BBC that filming for Block 5 had begun with Justin Molotnikov directing "Face the Raven", written by Sarah Dollard.

[49] On 1 July 2015, the BBC confirmed that Rachel Talalay would return to direct the final two episodes of the series, both written by Steven Moffat.

[50] Production blocks were arranged as follows:[43][51] On 9 July 2015, the first trailer for the series was released, alongside the confirmation of the airdate of "The Magician's Apprentice".

[1][2][3] Series 9 holds a 90% approval rating on online review aggregate site Rotten Tomatoes with an average score of 8.25/10.

The site's consensus reads "Peter Capaldi and the writers have settled into an emotionally engaging tone, allowing the show to raise the stakes for the Twelfth Doctor".