The sixteenth season of Doctor Who ran between 2 September 1978 and 24 February 1979. It consisted of six serials and twenty-six epsiodes. This season saw the introduction of the Black and White Guardians as well as the companion Romana I. This season is sometimes colloquially known as The Key to Time season after the story arc involving the Key to Time. Although not the first season to consist of linked stories (Season 8 in 1971 was the first, as all the stories that year featured the Master), it was the first to be recognised as having a series-long arc. Although multi-serial arcs would occur again, such a full-season experiment wouldn't be attempted again until Season 23.
Season 16 marked a triple milestone for Doctor Who: the hundredth story (The Stones of Blood), the five-hundredth episode (episode 1 of The Armageddon Factor) and the fifteenth anniversary of the first broadcast, on November 23, 1978.
In 2002 (Region 1) it became the first Doctor Who season to be released to DVD in its entirety in a single box set; it remained the only "classic series" season to be available as a single set until the release of Season 23, The Trial of a Time Lord to DVD in 2008.
Television stories
| # | Title | Writer | Episodes | Notes |
| 1 | The Ribos Operation | Robert Holmes | 4 | First appearance of Romana |
| 2 | The Pirate Planet | Douglas Adams | 4 | |
| 3 | The Stones of Blood | David Fisher | 4 | |
| 4 | The Androids of Tara | David Fisher | 4 | |
| 5 | The Power of Kroll | Robert Holmes | 4 | |
| 6 | The Armageddon Factor | Bob Baker Dave Martin |
6 | Final appearance of Mary Tamm as Romana; first appearance of the Black Guardian |
Main cast
- The Fourth Doctor - Tom Baker
- Romana - Mary Tamm (introduced The Ribos Operation)
- K9 - John Leeson (voice) (absent during The Power of Kroll)
Notes
- John Leeson, more well known as the voice of K9, appeared as the human Dugeen during The Power of Kroll.
- Lalla Ward guest stars as Princess Astra in The Armageddon Factor before taking over the role of Romana from Mary Tamm in Destiny of the Daleks.
Stories set during this season
- PDA: Tomb of Valdemar (between The Ribos Operation and The Pirate Planet)
- MA: The Shadow of Weng-Chiang (between The Stones of Blood and The Androids of Tara)
- PDA: Heart of TARDIS (between The Stones of Blood and The Androids of Tara)
- CC: Ferril's Folly (between The Stones of Blood and The Androids of Tara)
- DWAN: X-Rani and the Ugly Mutants (between The Androids of Tara and The Power of Kroll)
- DWAN: Light Fantastic (between The Androids of Tara and The Power of Kroll)
- DWAN: Reluctant Warriors (between The Androids of Tara and The Power of Kroll)
- DWAN: The Weapon (between The Androids of Tara and The Power of Kroll)
- DWAN: Return of the Electrids (between The Androids of Tara and The Power of Kroll)
- DWAN: The Sleeping Guardians (between The Androids of Tara and The Power of Kroll)
Adaptations and merchandising
Home media
VHS
- The Ribos Operation
- The Pirate Planet
- The Stones of Blood
- The Androids of Tara
- The Power of Kroll
- The Armageddon Factor
- The Tom Baker Years (excerpts from all stories)
DVD
This entire season was released with minimal restoration and extras in region 1 only on 1 October 2002 as a box set and was available individually. A limited edition box set with full restoration and expanded extras was released in region 2 on 24 September 2007. This limited edition version was later issued as the 7 November 2007 region 4 release, the 3 March 2009 region 1 "Special Edition" release (these were also available individually), and the 16 November 2009 non-limited region 2 re-release.
Novels
- Doctor Who and the Ribos Operation
- Doctor Who and the Stones of Blood
- Doctor Who and the Androids of Tara
- Doctor Who and the Power of Kroll
- Doctor Who and the Armageddon Factor
Target Books was unable to come to an agreement with Douglas Adams to novelise his script, The Pirate Planet, leaving it one of only a half-dozen classic-series episodes never adapted as a book.