The sixteenth season of Doctor Who ran between 2 September1978 and 24 February1979. It consisted of six serials and twenty-six episodes. 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.
A number of publicity photos for the season show Tom Baker sporting a very obvious bandage on his upper lip; this was due to his being bit by a dog shortly before filming for the season began. The resulting lip injury is visible to varying degrees throughout the season.
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.
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.