Nebulous is a post-apocalyptic science fiction comedy radio show written by Graham Duff and produced by Ted Dowd from Baby Cow Productions; it is directed by Nicholas Briggs. The series premiered in the United Kingdom on BBC Radio 4. Set in the year 2099 AD, the show focuses on the adventures of the eponymous Professor Nebulous, director of operations for the eco-troubleshooting team KENT (the Key Environmental Non-Judgmental Taskforce) as they combat various catastrophes and try to set the world back on the right path following a worldwide environmental disaster known as "The Withering". As well as being a parody of a number of famous science fiction programmes, including Doctor Who, Quatermass and Doomwatch, Nebulous is considered a cult radio programme, attracting a number of guest appearances from famous actors.

There have been three series of Nebulous; the first was broadcast between 6 January and 10 February 2005. The series was well received by critics, and a second series was broadcast between 5 April and 10 May 2006, with a third series commissioned by the BBC which began broadcasting on Thursday, 15 May 2008 at 23:00 BST. The first series was released on compact disc on 5 February 2007 by BBC Audio. Since 2009 all three series have been broadcast on BBC Radio 7. Duff has also announced that he is planning to make an animated series of Nebulous.