- Sigma Librae
- Sigma Niobe
- Sigma Niobe II
- Sigma Pavonis
- Sigma Pavonis IV
- Sigma Pegasi
- Sigma Quadrant
- Sigma Quadratis
- Sigma Serpentis
- Sigma Tama
- Sigma Tama IV
- Sigma Thernia
- Sigma Thernia III
- Sigma Thernia III-B
- Sigma Tricali
- Sigma V
- Sigma Zhukova
- Sigma class
- Sigma fishman
- Sigma ray
- Sigma system
- Sigmund Freud
- Sigmund booth
- Sign language
- Signal to Noise
- Signature Edition
- Signi Beta
- Signis Epsilon I
- Signs from Heaven
- Sigol Rusot
- Sigrengar
- Sigrid Thursen
- Sihanouk
- Siilar
- Sijioat
- Sik
- Sikaar
- Sikal
- Sikan and T'Risa
- Sikarian
- Sikarian Canon
- Sikarian sector
- Sikaris
- Sikaris III
- Sikh (Ensign)
- Sikhism
- Sikorn
- Sikrah
- Sikta
- Sil-Vo
- Sila
- Silaatkain
- Siladian
- Silaran Prin
- Silarian sector
- Silas
- Silas Griems
- Silas Jones
- Silash ch'Gesrit
- Silek
- Silent Cries
- Silent Enemy
- Silent Forrester
- Silent Weapons
- Silesi
- Silgos Prime
- Silgov
- Silica
- Silica Tare
- Silica Tare (planet)
- Silicasa
- Silicasca
- Silicon
- Silicon-based lifeform
- Silicon Avatar
- Silicon based dip
- Silicon creature of Centuri
- Silik
- Silik (Suliban)
- Silik (Vulcan)
- Silikh fly
- Silithium
- Silivar
- Silivis
- Silk
- Silky Way
- Sillerac
- Silne Koryn
- Silok
- Siloti
- Silotown
- Silva
- Silva La Forge
- Silva V
- Silvak Outpost
- Silvanus
- Silvanus I
- Silvanus II
- Silver
- SilverTail
- Silver (disambiguation)
- Silver Blood
- Silver Slipper
- Silver moss
- Silverberry
- Silverman
- Silverman (USS Excelsior)
- Silverspot
- Silvestra
- Silvet
- Silwaan
- Simak
- Simaks
- Simas
- Simave
- Simaya
- Simeon
- Simeta
- Similitude
- Simka Colony
- Simm
- Simmerith
- Simok
- Simon
- Simon-316
- Simon (Captain)
- Simon (King)
- Simon (Orion)
- Simon Anders
- Simon Anderson
- Simon Grayson
- Simon Hawke
- Simon Nordell
- Simon Rigg
- Simon Tarses
- Simon Van Gelder
- Simon Van Gelder (mirror)
- Simon and MacMillan Books
- Simone
- Simone (Class F)
- Simone (Enochian)
- Simone (Human)
- Simone Van Gelder
- Simora
- Simpalla
- Simparri
- Simperia (planet)
- Simpson
- Simpson (disambiguation)
- Simri
- Simton
- Simus
- Sinai National Preserve
- Sinai Planum
- Sinak
- Sinak (22nd century)
- Sinak (23rd century)
- Sinbad (disambiguation)
- Sinbad IV
- Sinchante Jin
- Sinclair
- Sinclair (Lieutenant)
- Sind
- Sindar
- Sindareen
- Sindarius
- Sindikash
- Sindikash 1-4 Transport
- Sindorin
- Sinek
- Sines
- Sing
- Singapore
- Singfer Nebula
- Singh
- Singh (Admiral)
- Singh (USS Enterprise)
- Singh (engineer)
- Singh (merchant)
- Singh (security)
- Singh el Bashir
- Singha
- Singha (Bajor)
- Singha (planet)
- Singha (starship)
- Singha refugee camp
- Singin' in the Rain
- Single Integrated Operational Plan
- Singleton Air Force Base
- Singularity
- Singularity (episode)
- Singularity (short story)
- Singularity II
- Singularity One
- Singularity bomb
- Singularity plant
- Singularity system
- Singularity torpedo
- Siniki
- Sinisser
- Sinjin Kirk
- Sinkonnen
- Sinna
- Sinnawa Lotos
- Sinnit Arvid
- Sinnravian
- Sinoraptor
- Sinqay
- Sins of Commission
- Sins of the Father
- Sins of the Fathers
- Sins of the Mother
- Sinterka
- Sinuiji
- Sinuiji system
- Siobhan
- Siobhan Bryn
- Sioux
- Sioux (disambiguation)
- Sioux City
- Siouxsie
- Sipak
- Sir'vara
- Sira
- Sirahna
- Siras
- Sirav
- Siraven Resort
- Siregar
- Sirel Terraforming
- Sirella
- Sirella (mirror)
- Siren
- Siren's Song
- Siren (myth)
- Sirenia
- Sirhc
- Sirhc Turren (23rd century)
- Siri
- Sirian Robotics
- Siriex Apparatus
- Sirillium
- Sirius
- Sirius (disambiguation)
- Sirius (planet)
- Sirius A
- Sirius IV
- Sirius X
- Sirius class
- Sirius sector block
- Sirix
- Sirloin
- Sirna Kolrami
- Sirok
- Sirol
- Sirri Rand
- Sirrie
- Sirrie IV
- Sirsa III
- Sirta D'Qua
- Sirtis Nebula
- Siruzav
- Siryk
- Siryk Variations
- Sisara
- Sisko
- Sisko's Creole Kitchen
- Sisko's baseball
- Sisko's house
- Sisko family
- Sisor
- Sisra Koas
- Sisterson
- Sisus
- Sisyphos
- Sisyphus
- Sisyphus (continent)
- Sisyphus (disambiguation)
- Sita Mohindas
- Sitak
- Sitar
- Sitar (instrument)
- Sitar (scientist)
- Sitar class
- Sitav
- Site Extension
- Site wej
- Sith Har
- Sith Har Blaster
- Sithala
- Sitkoskir
- Sitlas
- Sito Jaxa
- Sito Jaxa (mirror)
- Sito Keral
- Sitok
- Sitok (22nd century)
- Sitok (24th century)
- Sitok upgrade
- Sitora
- Situla I
- Siva
- Siva class
- Sivadeki
- Sivak
- Sivao
- Sivaoan
- Sivath
- Siveb
- Sivek
- Sivista class
- Sivok
- Six-Day War
- Six Branch
- Six Lubak
- Six Orbs of Choiza
- Sixan
- Sixth Fleet
- Sixth planets
- Sizing scanner
- Siziu
- Sizox
- Sizzle bug
- Sja-Yo
- Skagara
- Skagaran
- Skagaran colony
- Skagaran whiskey
- Skagway
- Skal Torr
- Skalaar
- Skaliir
- Skamandros
- Skamda
- Skardal
- Skaren
- Skarl
- Skaroskar
- Skastra
- Skat knife
- Skateboard
- Skatemus
- Skav
- Skaxzss
- Skedan