Doctor Who is a British science fiction television programme produced by the BBC. As of 25 December 2017,[update] 840 episodes of Doctor Who have aired, concluding the tenth series. This includes one television movie and multiple specials, and encompasses 276 stories over 36 seasons. Additionally, four charity specials and two animated serials have also been aired. The programme's high episode count has resulted in Doctor Who holding the world record for the highest number of episodes of a science-fiction programme. In June 2017, it was announced that due to the terms of a deal between BBC Worldwide and SMG Pictures in China, the company has first right of refusal on the purchase for the Chinese market of future series of the programme until and including Series 15.
Doctor Who ceased production in 1989, then resumed in 2005. The original series (1963–1989), generally consists of multi-episode serials; in the early seasons, and occasionally through its run, serials tend to link together, one story leading directly into the next. The 2005 revival trades the earlier serial format for a run of self-contained episodes, interspersed with occasional multi-part stories and structured into loose story arcs.
For the first two seasons of Doctor Who and most of the third (1963–1966), each episode carries its own title; the show displays no titles for overarching serials until The Savages, at which point the episodic titles cease. The below titles for these early serials are those in most common circulation, used for commercial releases and in resources such as the Doctor Who Reference Guide and the BBC's classic episode guide. The practice of individual episode titles resurfaces in the show's 2005 revival, with its altered story structure compared to the 20th century production.
Due to the BBC's 1970s junking policy, 97 episodes of Doctor Who from the 1960s are no longer known to exist. As a result, 26 serials are currently incomplete, with one or more episodes represented only by audio and, in many cases, clips or still frames. For commercial release, some episodes have been reconstructed using off-air audio recordings, paired to surviving visuals or newly-commissioned animation.