Doctor Who is a British science fiction television series broadcast by the BBC since 1963. The series, created by Sydney Newman, C. E. Webber, and Donald Wilson, depicts the adventures of an extraterrestrial being called the Doctor, part of a humanoid species called Time Lords. The Doctor travels in the universe and in time using a time travelling spaceship called the TARDIS, which externally appears as a British police box. While travelling, the Doctor works to save lives and liberate oppressed peoples by combating foes. The Doctor often travels with companions. Beginning with William Hartnell, fourteen actors have headlined the series as the Doctor; as of 2023, Ncuti Gatwa leads the series as the Fifteenth Doctor. The transition from one actor to another is written into the plot of the series with the concept of regeneration into a new incarnation, a plot device in which, when a Time Lord is fatally injured, their cells regenerate and they are reincarnated. Each actor's portrayal is distinct, but all represent stages in the life of the same character and, together, they form a single lifetime with a single narrative. The time-travelling nature of the plot means that different incarnations of the Doctor occasionally meet. In 2017, Jodie Whittaker became the first woman to be cast in the lead role as the Thirteenth Doctor. The series is a significant part of popular culture in Britain[1] and elsewhere; it has gained a cult following. It has influenced generations of British television professionals, many of whom grew up watching the series.[2] Fans of the series are sometimes referred to as Whovians. The series has been listed in Guinness World Records as the longest-running science-fiction television series in the world,[3] as well as the "most successful" science-fiction series of all time, based on its overall broadcast ratings, DVD, and book sales.[4] The series 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 series was relaunched in 2005 and was produced in-house by BBC Wales in Cardiff. Since 2023, the show is co-produced by Bad Wolf and BBC Studios Productions in Cardiff. Doctor Who has also spawned numerous spin-offs, including comic books, films, novels, and audio dramas, and the television series Torchwood (2006–2011), The Sarah Jane Adventures (2007–2011), K9 (2009–2010), and Class (2016). It has been the subject of many parodies and references in popular culture.