Sigma

;Astronomical nomenclature
* Sigma X, a planet
* Sigma Antares sector
* Sigma Coronae Borealis, a star system
* Sigma Draconis star system
** Sigma Draconis I, a planet
** Sigma Draconis II, a planet
** Sigma Draconis III, a planet
*** Sigma Draconis III native, a species
** Sigma Draconis IV, a planet
*** Sigma Draconis IV native, a species
*** Sigma Draconis IV Tourist Center
** Sigma Draconis V, a planet
** Sigma Draconis VI, a planet
*** Sigma Draconis VI native, a species
** Sigma Draconis VII, a planet
** Sigma Draconis VIII, a planet
** Sigma Draconis IX, a planet
* Sigma Erandi system (aka Sigma Erani system)
* Sigma III solar system
** Quadra Sigma III, a planet
* Sigma Iotia, a star system
** Sigma Iotia II, a planet
* Sigma Nelvana, a star
* Sigma Nesterowitz, a location
* Sigma Serpentis, a star system
* Sigma Tama IV, a planet
* Sigma Trotti, a location
;Security terms
* Sigma 9 clearance, a top-level security clearance
* "Tuvok-Sigma-4", authorization code
fr:Sigma