played by John Leeson (voice)

Also played by David Brierly (Season 17)

K-9 joined the TARDIS when his original owner, Professor Marius, was unable to bring him back to Earth due to luggage limits. K-9 was a robotic dog which functioned as a mobile computer/defence system.

K-9 Mk I stayed with Leela on Gallifrey, the Doctor produced a K-9 Mk II, which remained in E-Space with Romana.

K-9 Mk III was a gift from the Doctor to Sarah Jane Smith.

K-9 Mk IV was also a gift from the Doctor to Sarah Jane Smith when K-9 Mk III was destroyed in an explosion.

First regular appearance: The Invisible Enemy

Final regular appearance: Warriors' Gate

K-9 has met the following Doctors
K-9 has appeared in the following adventures
Addiional information about K-9
  • Home (Mark I): Bi-Al Foundation
  • Home (Mark II): The TARDIS
  • Home (Mark III): London, Earth (20th century)
  • Home (Mark IV): London, Earth (21st century)