State of Decay (1980) is a four-part serial in the science fiction television series Doctor Who, starring Tom Baker as the Doctor and Lalla Ward and Matthew Waterhouse as the Doctor's companions Romana and Adric respectively.

This story is one of a series of three that takes place in E-Space. The Doctor and his companins arrive at a planet ruled by three Lords named Zargo, Camilla and Aukon, vampire servants to the last of the Great Vampires.

The story was written by Terrance Dicks and directed by Peter Moffatt. The cast also includes Emrys James (Aukon), Rachel Davies (Camilla), William Lindsay (Zargo), Clinton Greyn (Ivo), Rhoda Lewis (Marta) and Thane Bettany (Tarak).

The serial was novelised as Doctor Who and the State of Decay by Terrance Dicks in 1981.

See also List of Doctor Who serials