Jenny, portrayed by Georgia Moffett, is a fictional character in the long-running British science fiction television series Doctor Who. She appeared in the episode "The Doctor's Daughter", originally broadcast 10 May 2008. Jenny is the daughter of the series protagonist the Doctor, a product of altered DNA extracted from a tissue sample of his tenth incarnation's hand. The character was created by writer Stephen Greenhorn.

Georgia Tennant (then-Moffett) was cast as Jenny after auditioning for a smaller part in the episode "The Unicorn and the Wasp", and impressing the series producers. The character was generally well received by reviewers, with many speculating that she would return to the franchise. Moffett also expressed an interest in this possibility.

The fictional Doctor's daughter was played by a real Doctor's daughter; actress Georgia Moffett (her father's legal surname) is the daughter of actor Peter Davison, who portrayed the Doctor's fifth incarnation from 1981 to 1984. Moffett met David Tennant – playing the tenth incarnation of the Doctor – on the set; they began a relationship, and married in 2011, when she changed her name to Georgia Tennant.

When the Doctor's time travelling TARDIS is drawn to the planet Messaline, his DNA is used by warring human soldiers on the planet in a Progenation Machine, a device that instantly creates a fully grown and educated new person, and the Doctor recognises her as his "daughter". Born a fighter, with combat skills and tactics automatically programmed, she is initially ideologically at odds with the Doctor's pacifism, but after learning she has two hearts and is connected to the near-extinct race of Time Lords, she begins to pattern her behaviour on that of her parent.

Named "Jenny" by the Doctor's companion Donna (Catherine Tate) as she is a "generated anomaly", she is initially received with ambivalence by the Doctor, whom she reminds of the loss of his previous family. He eventually warms to her, and welcomes her aboard his crew as a companion. Just as peace appears to have been restored between the planet's warring factions, Jenny is shot and apparently killed. The Doctor cradles her dying form in his arms, and is visibly distraught when she does not revive or regenerate from the wound. In the episode's closing scenes after the Doctor leaves, Jenny revives, takes a small spaceship, and takes off into the unknown to become an explorer like her parent.

In the accompanying Doctor Who Confidential episode, David Tennant (who portrays the Doctor) refers to her as "another member of that race, or something closely akin to it." In the episode itself the Doctor says to Jenny, "You're an echo, that's all. A Time Lord is so much more. A sum of knowledge, a code, shared history, shared suffering", but later accepts her as his daughter, saying "You're going to be more than great; you're going to be amazing". Jenny's 'death' is shown during "Journey's End" when the Doctor recalls those who have died while helping him, as he did not know she revived.

While it is well established within Doctor Who that the Doctor once had a family—his first incarnation having travelled with his granddaughter, Susan—this fact has been seldom referenced in the show. As executive producer Russell T Davies stated, when discussing the creation of Jenny as the Doctor's newest family member: "In the current series once or twice we've had fleeting little mentions, he said to Rose in the TARDIS in "Fear Her" that he'd been a father once. And now obviously this story, it's not a natural, biological daughter, you could argue, but this really brings him face to face with fatherhood."

Regarding the creation of the character Jenny, series producer Phil Collinson explained, "It came out of a desire to keep pushing David, and keep taking him in new directions, and keep challenging him, really. To suddenly find himself with a member of family is kind of one of the biggest challenges you could give him, so I'm chuffed we did it." Moffett has agreed that giving the character a daughter was "an interesting, emotional, dramatic place for the character to go," while the episode's writer, Stephen Greenhorn, has spoken of the manner in which creating Jenny allowed the show to broach "aspects of the Doctor's past life that we don't often get to discuss, about his previous family that he had and lost in the Time War." Steven Moffat suggested that the character lives in the episode's conclusion.