The Sixth Doctor is the sixth incarnation of the protagonist

Doctor (Doctor Who)

The Doctor is the central character in the long-running BBC television science-fiction series Doctor Who, and has also featured in two cinema feature films, a vast range of spin-off novels, audio dramas and comic strips connected to the series....

 of the long-running BBC

BBC

The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...

 television science-fiction

Science fiction on television

Science fiction first appeared on a television program during the Golden Age of Science Fiction. Special effects and other production techniques allow creators to present a living visual image of an imaginary world not limited by the constraints of reality; this makes television an excellent medium...

 series Doctor Who

Doctor Who

Doctor Who is a British science fiction television programme produced by the BBC. The programme depicts the adventures of a time-travelling humanoid alien known as the Doctor who explores the universe in a sentient time machine called the TARDIS that flies through time and space, whose exterior...

. He was portrayed by Colin Baker

Colin Baker

Colin Baker is a British actor who is known for playing Paul Merroney in The Brothers from 1974 to 1976 and as the sixth incarnation of the Doctor in the long-running science fiction television series Doctor Who, from 1984 to 1986.- Background:Colin Baker was born in London, but moved north to...

. Although his televisual time on the series was comparatively brief and turbulent, Baker has continued as the Sixth Doctor in Big Finish

Big Finish Productions

Big Finish Productions is a British company that produces books and audio plays based, primarily, on cult British science fiction properties...

's range of original Doctor Who audio adventures.

Within the series' narrative, the Doctor is a centuries-old Time Lord

Time Lord

The Time Lords are an ancient extraterrestrial race and civilization of humanoids in the British science fiction television series Doctor Who, of which the series' eponymous protagonist, the Doctor, is a member...

 alien from the planet Gallifrey who travels in time and space in his TARDIS

TARDIS

The TARDISGenerally, TARDIS is written in all upper case letters—this convention was popularised by the Target novelisations of the 1970s...

, frequently with companions.