played by
John Leeson (voice)

K-9 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 also appeared in:

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)

K-9 has met the following Doctors: