Vislor Turlough

Vislor Turlough is a fictional character played by Mark Strickson in the long-running British science fiction television series Doctor Who. He was a companion of the Fifth Doctor, being a regular in the programme from 1983 to 1984. Turlough is an alien from the planet Trion who seeks to kill the Fifth Doctor on orders from the antagonist known as the Black Guardian. Turlough later chooses to side with the Doctor, accompanying him until Turlough's departure from the series in the 1984 serial Planet of Fire.

Turlough was created during a script meeting with script editor Eric Saward, who liked the concept of a companion who existed to try and kill the Doctor. Strickson was requested to be cast in the part by his agent, and was one of the last actors producer John Nathan-Turner saw in the auditions for Turlough's character. Nathan-Turner enjoyed Strickson's performance and offered him the part, with Strickson turning down a potential role in the series Angels to appear in Doctor Who.

Turlough's role in the series was criticized by literary critic John Kenneth Muir, who believed Turlough to be underdeveloped despite Strickson's good acting performance. Other critics felt the character's writing quality varied, though he has received analysis in the book Who is Who?, which analyzed his development as a result of his interactions with the Doctor.