The First Doctor is the initial 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 the actor William Hartnell

William Hartnell

William Henry Hartnell was an English actor. During 1963-66, he was the first actor to play the Doctor in the long-running BBC science fiction television series Doctor Who.-Early life:...

 from 1963 to 1966. Hartnell reprised the role in the tenth anniversary story The Three Doctors in 1973 - albeit in a reduced capacity due to his ailing health. Actor Richard Hurndall

Richard Hurndall

Richard Gibbon Hurndall was an English actor.-BBC radio:Hurndall was born in Darlington and he attended Claremont Preparatory School, Darlington and Scarborough College, before training as an actor at the Royal Academy of Dramatic Arts. He then appeared in several plays at Stratford-upon-Avon...

 played the part of the First Doctor in the 20th anniversary story The Five Doctors

The Five Doctors

The Five Doctors is a special feature-length episode of the British science fiction television series Doctor Who, produced in celebration of the programme's twentieth anniversary. It had its world premiere in the United States, on the Chicago PBS station WTTW and various other PBS member stations...

after William Hartnell's death in 1975.