The Tenth Doctor is the tenth incarnation of the protagonist of the long-running BBC television science-fiction series Doctor Who. He is played by David Tennant.
In the series’ narrative, the Doctor is a centuries-old Time Lord alien from the planet Gallifrey who travels in time in his TARDIS, frequently with companions. When the Doctor is critically injured, he can regenerate his body; in doing so, his physical appearance and personality change. Tennant portrays the tenth such incarnation, an eccentric, but daring man who will stop at nothing to save the universe.
This incarnation’s companions have included working class shop assistant Rose Tyler (Billie Piper), medical student Martha Jones (Freema Agyeman) and fiery temp worker Donna Noble (Catherine Tate); he eventually parts ways with them all by the end of the 2008 series finale, “Journey’s End”, after which he attempted to travel alone for the duration of the 2008-10 specials. Source - Wikipedia