Doctor Who is a long-running British science fiction television programme (and 1996 television movie) produced by the BBC about the adventures of a mysterious time-traveller known as "the Doctor", who explores time and space with his companions, solving problems and righting wrongs.

The programme is listed in the Guinness Book of World Records as the longest-running science fiction television series in the world and is also a significant part of British popular culture. It has been recognised for its imaginative stories, creative low-budget special effects during its original run and pioneering use of electronic music (originally produced by the BBC Radiophonic Workshop). In Britain and elsewhere, the show has become a cult television favourite and has influenced generations of British television professionals, many of whom grew up watching the series. It has received recognition from critics and the public as one of the finest British television programmes, including a BAFTA Award for Best Drama Series in 2006.

The programme originally ran from 1963 to 1989. A television movie was made in 1996, and the programme was successfully relaunched in 2005, produced in-house by BBC Wales. (Some development money for the new series is contributed by the Canadian Broadcasting Corporation (CBC), which is credited as a co-producer, although they do not have creative input into the show.) Doctor Who has also spawned spin-offs in multiple media, including the current television series Torchwood and The Sarah Jane Adventures.

The show's lead role is currently portrayed by David Tennant. A Christmas special co-starring Kylie Minogue will air in December 2007, and a fourth series, scheduled to air in 2008, is in production. For that series, Catherine Tate will reprise her role of Donna Noble, from the 2006 Christmas special, as the Doctor's latest companion. Midway through the series, Freema Agyeman will also return to her role of Martha Jones, following a multi-episode guest appearance in the Doctor Who spin-off series, Torchwood. John Barrowman will be filming for the show after Christmas 2007, reprising his role as Captain Jack Harkness, and Billie Piper will return as Rose Tyler for three episodes.

After a 2008 Christmas special and three further specials starring David Tennant, scheduled to air in 2009, Doctor Who is planned to return in 2010 for a fifth full length series.