The Adventures of K9

The Adventures of K9 was a series of four illustrated paperback storybooks for children written by David Martin and published by Sparrow Books together on 20 October 1980. The four books feature K9, the character Martin co-created. The books were written in conjunction with a planned but unmade K9 animated series. Specifically, the stories feature what is most likely to be K9 Mark I and seemingly take place sometime after the events of The Invasion of Time when the Doctor left K9 on Gallifrey.

The books include prefaces that indicate that K9 is working on behalf of the Time Lords. They also suggest that the Doctor's real name might be the Theta Sigma nickname heard in The Armageddon Factor and The Happiness Patrol.

In 2013, an audio anthology was released collecting all four stories.