Doctor Who is a British science fiction television program produced by the BBC since 1963. The program depicts the adventures of a Time Lord called "the Doctor", an extraterrestrial being, to all appearances human, from the planet Gallifrey. The Doctor explores the universe in a time-traveling space ship called the TARDIS. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Accompanied by a number of companions, the Doctor combats a variety of foes while working to save civilizations and help people in need.
The show is a significant part of British popular culture, and elsewhere it has gained a cult following. It has influenced generations of British television professionals, many of whom grew up watching the series. The program originally ran from 1963 to 1989. There was an unsuccessful attempt to revive regular production in 1996 with a backdoor pilot, in the form of a television film titled Doctor Who. The program was relaunched in 2005, and since then has been produced in-house by BBC Wales in Cardiff. Doctor Who has also spawned numerous spin-offs, including comic books, films, novels, audio dramas, and the television series Torchwood (2006–2011), The Sarah Jane Adventures (2007–2011), K-9 (2009–2010), and Class (2016), and has been the subject of many parodies and references in popular culture.
Thirteen actors have headlined the series as the Doctor. The transition from one actor to another is written into the plot of the show with the concept of regeneration into a new incarnation, a plot device in which a Time Lord "transforms" into a new body when the current one is too badly harmed to heal normally. Each actor's portrayal is unique, but all represent stages in the life of the same character. Together, they form a single lifetime with a single narrative. The time-traveling feature of the plot means that different incarnations of the Doctor occasionally meet. The Doctor is currently portrayed by Jodie Whittaker, who took on the role after Peter Capaldi's exit in the 2017 Christmas special "Twice Upon a Time".