Doctor Who season 18

Doctor Who
Season 18
Cover art of the Blu-ray release for the complete season
Starring	Tom Baker Lalla Ward John Leeson Matthew Waterhouse Sarah Sutton Janet Fielding
No. of stories	7
No. of episodes	28
Release
Original network	BBC1
Original release	30 August 1980 (1980-08-30) – 21 March 1981 (1981-03-21)
Season chronology
← Previous Season 17 Next → Season 19
List of episodes

The eighteenth season of British science fiction television series Doctor Who consisted of seven four-episode serials broadcast from 30 August 1980 with the serial The Leisure Hive, to 21 March 1981 with the serial Logopolis. The season is Tom Baker's final as the Fourth Doctor before his regeneration into the Fifth Doctor (Peter Davison), as well as Lalla Ward's as companion Romana II and John Leeson's as the voice of K9. For the second time (The first being during Season 4 and third being Season 21), the entire main cast changed over the course of a single season. The season also sees the debut of Matthew Waterhouse as Adric, Sarah Sutton as Nyssa, and Janet Fielding as Tegan Jovanka, the three of whom would remain regular companions into the Fifth Doctor's era, as well as the return of the Master, portrayed both by Geoffrey Beevers and Anthony Ainley.

The season was the first to be produced by John Nathan-Turner, who would produce every season of the show until 1989, and the first to feature script editor Christopher H. Bidmead. The season features a trilogy of connected serials, Full Circle, State of Decay, and Warrior's Gate, which form a trilogy set in a "bubble universe" called E-Space,^[1] as well as The Keeper of Traken and Logopolis, the first two serials of a trilogy continued in season 19's Castrovalva, centred on the return of The Master and the regeneration of the Fourth Doctor.^[2]