Series 1

The Ninth Doctor is an incarnation of the Doctor, the protagonist of the BBC science fiction television series Doctor Who.

Christopher Eccleston plays the Doctor.

Series 2, 3 and 4

The Tenth Doctor is an incarnation of the Doctor, the protagonist of the BBC science fiction television series Doctor Who.

David Tennant plays the Doctor.

Series 5, 6 and 7

The Eleventh Doctor is an incarnation of the Doctor, the protagonist of the BBC science fiction television series Doctor Who..

Matt Smith plays the Doctor.

Series 8

The Twelfth Doctor is an incarnation of the Doctor, the protagonist of the BBC science fiction television series Doctor Who.

Peter Capaldi plays him.