The Fugitive Doctor is an incarnation of the Doctor, the protagonist of the British science fiction television series Doctor Who. She is portrayed by Jo Martin, the first black actor to play the Doctor. The character first appeared in the twelfth series of the programme's revival in "Fugitive of the Judoon" (2020), where she was disguised as a woman named Ruth Clayton in 21st century Gloucester. Eventually, she restores her memories, and it is revealed that Ruth is an incarnation of the Doctor, though her placement in the chronology of the series is initially unclear.

Within the programme's narrative, the Doctor is a Time Lord, from the planet Gallifrey. The Doctor travels in a time-travelling space ship, the TARDIS. Possessing alien physiology, the Doctor, when critically injured, can regenerate into a new body, gaining a new physical appearance and personality. This plot device has allowed a number of actors, both male and female, to portray the Doctor through the decades. Each actor to play the Doctor offers a different take on the Doctor's essential personality. A fugitive, this incarnation of the Doctor is considered to be a more ruthless incarnation, and formerly worked for Time Lord black ops group "The Division", from whom she is now on the run.

This incarnation was conceived by showrunner Chris Chibnall and co-writer Vinay Patel, with the pair coming up with the incarnation late into writing the script of "Fugitive of the Judoon". The Fugitive Doctor was included not only to foreshadow the upcoming "Timeless Child" arc of series 12, but also to act as a surprise twist within "Fugitive of the Judoon". The incarnation would go on to reappear multiple times within the show following her debut.

The Fugitive Doctor received a mostly positive reception from critics, who praised the casting of a black woman as the Doctor and highlighted the performance of Martin. Many fans and critics expressed interest in seeing Martin reprise the role in a larger capacity. Some critics criticised the usage and execution of the character's concept within the series. Martin has expressed interest in continuing to portray the role, and has appeared in several Big Finish Productions audio dramas depicting stories starring the Fugitive Doctor. She has also stated that the role had helped her expand her career prospects, particularly in America.

The Fugitive Doctor first appears in the 2020 episode "Fugitive of the Judoon", disguised as human tour guide Ruth Clayton by means of a Chameleon Arch. As Ruth, she lives alongside her "husband" Lee in 21st century Gloucester with Ruth having no knowledge of her true nature. Intergalactic alien police force the Judoon locate her and invade the city, intending to present her to Galifreyan Commander Gat, who plans to return the Doctor to Gallifreyan black ops group the Division after the Doctor fled from them. Lee, companion to the Fugitive Doctor and a fellow Time Lord, directs Ruth to a lighthouse, where her memories are restored. At the same time, the Thirteenth Doctor finds a police box buried in the grounds – Ruth's TARDIS. As they reveal their identities to one another, it transpires that neither Doctor recognises the other, leading to confusion between the pair as they both assumed the other was a future version of herself. After tricking Gat into accidentally killing herself with a malfunctioning gun, the Fugitive Doctor parts with the Thirteenth Doctor acrimoniously.

She reappears briefly in "The Timeless Children", when the Thirteenth Doctor is trapped in the Time Lord storage database the Matrix by the Master. He informs her that she is the Timeless Child, and had lived many lives prior to what she believed to be her first incarnation. In trying to escape and reconcile this knowledge with her identity, she encounters a projection of the Fugitive Doctor. The projection reminds her that she has never previously been defined by her past before disappearing.

The Fugitive Doctor reappears in "Once, Upon Time". In that episode, the Thirteenth Doctor experiences flashbacks to a raid by the Fugitive Doctor on a location known as the Temple of Atropos, where the Fugitive Doctor confronted the Ravagers known as Swarm and Azure. The Thirteenth Doctor learns that the Fugitive Doctor had led a team of Division operatives, including the Lupari officer Karvanista, to capture the two Ravagers and uses her past self's methods as an inspiration to resolve a situation involving the Ravagers in the future.

The Fugitive Doctor reappears in "The Power of the Doctor" as an AI hologram which is used to trick the Master after he has stolen the Doctor's body. The Fugitive Doctor is later seen as a memory from a past adventure involving Anansi and his daughter Abena in the Fifteenth Doctor story, "The Story & the Engine".