"Ascension of the Cybermen" is the ninth and penultimate episode of the twelfth series of the British science fiction television programme Doctor Who, first broadcast on BBC One on 23 February 2020. It was written by Chris Chibnall, and directed by Jamie Magnus Stone. It is the first of a two-part story; the concluding episode "The Timeless Children", the finale of the twelfth series, aired on 1 March.

The episode features Jodie Whittaker as the Thirteenth Doctor as she deals with the aftermath of her actions in "The Haunting of Villa Diodati". When the Doctor becomes separated from her companions Graham O'Brien, Ryan Sinclair and Yasmin Khan, portrayed by Bradley Walsh, Tosin Cole and Mandip Gill respectively, the team must face the consequence of the deadly Cyber-Wars, banding together with the last humans as they defend themselves from the Cybermen and search for a way out.

The episode was watched by 4.99 million viewers, and received positive reviews from critics.

Bradley Walsh who plays Graham said that the Ascension of the Cybermen was his favourite episode. “This episode by a country mile is my favourite", he remarked in a behind-the-scenes video. "It was great. It was like making a real blockbuster movie” ^[1]

In rural Ireland during the early 20th century, a young couple find and adopt an abandoned baby, Brendan, who grows up to be a police officer. On an early assignment, he is shot and falls off a cliff during a confrontation with a criminal, but miraculously survives unscathed. Years later, he retires but is confronted by his adoptive father and mentor, both of whom haven't aged, and they wipe his memory.

In the far future, the last of humanity is hiding from the last of the Cybermen, who have hunted them almost to extinction. As a pair of Cybershuttles arrive overhead, the Doctor and her companions arrive and attempt but fail to protect them, and some of the humans are killed. The Doctor orders her companions to leave with the remaining humans on their ship, and get to safety, but Ryan and another human named Ethan are separated by the Cybermen's only partially cyberconverted leader, Ashad. Ryan and Ethan escape to assist the Doctor in hijacking one of the Cybershuttles, but the Cybermen pursue in another Cybershuttle.

In deep space, Yaz, Graham, and the other three humans Yedlarmi, Ravio and Bescot discover they are traveling through a battlefield surrounded by dead Cybermen. They board an abandoned Cybercarrier, a large Cyberman ship, which they believe can take them to "Ko Sharmus", a haven which is supposedly home to the Boundary, a portal that sends humans to the other side of the universe where they cannot be reliably followed by the Cybermen. Graham and Ravio investigate and discover the Cybercarrier holds thousands of fresh Cybermen warriors in stasis just as Ashad and his crew dock their shuttle.

The Doctor, Ryan, and Ethan arrive on the planet where Ko Sharmus is. They discover Ko Sharmus is a person who helped other humans through the Boundary but remained behind as a ferryman in case others had survived. He takes them to the Boundary, and a portal opens. Ashad and the Cybermen begin drilling into the warriors and resurrecting them, while Graham and Ravio return to the control deck. Ashad leads the warriors to the control deck as Yaz manages to contact the Doctor, warning her that the ship is almost there, but it is carrying numerous warriors.

The Doctor watches in horror, as the other side of the portal reveals the ruined Gallifrey, much to everyone's confusion. The Master leaps through, exclaiming that the Doctor should be afraid because everything is about to change forever.