Sigma

Sigma may refer to:
* Ood Sigma (TV: Planet of the Ood)
* Sigma (letter)
* Sigma (planet) (COMIC: The Fabulous Idiot)
* Earl Sigma (TV: The Happiness Patrol)
* Theta Sigma (TV: The Armageddon Factor, The Happiness Patrol, COMIC: Flashback)
* Survey Ship Sigma (COMIC: The Dalek Project)