- Saci (Brazilian) – One-legged nature spirit
- Sack Man (Worldwide)
- Sagari (Japanese) – Horse head that dangles from trees on Kyūshū
- Sakabashira (Japanese) – Haunted pillar, installed upside-down
- Salamander (Alchemy) – Fire elemental
- Samebito (Japanese) – Shark-man servant of the dragon king of the sea
- Samodiva (Slavic) – Nature spirit
- Sampati (Hindu) – The demigod Jatayu's brother
- Sandman (Northern Europe) – Nursery spirit that induces sleep in children
- Sango (South Western Nigeria) – Yoruba king of arts, music, dance and entertainment
- Santelmo (Philippine) – Spirits in the form of fireballs that roam around the forest
- Santa Claus (North Pole-European folklore) – Elderly man who delivers gifts to well-behaved children on the night of Christmas Eve
- Sânziană (Romanian) – Nature spirit
- Sarimanok (Philippine) – Bird of good fortune
- Sarngika (Hindu) – Bird spirit
- Sarugami (Japanese) – Wicked monkey spirit who was defeated by a dog
- Satori (Japanese) – Mind-reading humanoid
- Satan (Heaven-Abrahamic mythology) – Ruler of Hell
- Satyr (Greek) – Human-goat hybrid and fertility spirit
- Satyrus (Medieval Bestiary) – Apes who always bear twins, one the mother loves, the other it hates
- Sazae-oni (Japanese) – Shapeshifting turban snail spirit
- Sceadugenga (English) – Shapeshifting undead
- Scitalis (Medieval Bestiaries) – Snake which mesmerizes its prey
- Scorpion Man (Sumerian) – Human-scorpion hybrid
- Scylla (Greek) – Human-snake hybrid with a snake's tail, twelve legs, and six long-necked snake heads
- Sea-bee (Heraldic) – Fish-tailed bee
- Sea-lion
- Sea monk (Medieval folklore) – Fish-like humanoid
- Sea monster (Worldwide) – Giant, marine animals
- Sea serpent (Worldwide) – Serpentine sea monster
- Sea-Wyvern (Heraldic) – Fish-tailed wyvern
- Seko (Japanese) – Water spirit which can be heard making merry at night
- Selkie (Faroese, Icelandic, Irish, and Scottish) – Human-seal shapeshifter
- Senpoku-Kanpoku (Japanese) – Human-faced frog which guides newly deceased souls to the graveyard
- Seps (Medieval Bestiaries) – Snake with corrosive venom
- Serpent (Worldwide) – Snake spirit
- Serpopard (Ancient Egypt) – Serpent-leopard hybrid
- Shachihoko (Japanese) – Tiger-carp hybrid
- Shade (Worldwide) – Spiritual imprint
- Shadow People (American) – Malevolent ghost
- Shahbaz (Persian) – Giant eagle or hawk
- Shaitan (Islam) – Islamic version of the Devil (Satan) from the Bible
- Shang-Yang (Chinese) – Rain bird
- Shapeshifter
- Shedim (Jewish) – Chicken-legged demon
- Shedu (Akkadian and Sumerian) – Protective spirit who takes the form of a winged bull or human-headed lion
- Shellycoat (English, Scottish and German, as schellenrocc) – Water spirit
- Shen (Chinese) – Shapeshifing sea monster
- Shenlong (Chinese) – Weather dragon
- Shibaten (Japanese) – Water spirit from Shikoku
- Shikigami (Japanese) – Servant spirit
- Shiki-ōji (Japanese) – Child-sized servant spirit
- Shikome (Japanese) – Underworld hag
- Shinigami (Japanese) – "Death god"
- Shiro-bōzu (Japanese) – White, faceless spirit
- Shirouneri (Japanese) – Animated mosquito netting or dust cloth
- Shiryō (Japanese) – Spirit of a dead person
- Shisa (Japanese) – Lion-dog hybrid
- Shishi (Chinese) – Protective animal
- Shōjō (Japanese) – Red-haired sea-sprites who love alcohol
- Shōkera (Japanese) – Creature that peers in through skylights
- Shtriga (Albanian) – Vampire witch that feeds on children
- Shui Gui (Chinese) – Drowned ghost
- Shug Monkey (English) – Dog/monkey
- Shunoban (Japanese) – Red-faced ghoul
- Shuten-dōji (Japanese) – Ruler of the Oni
- Sídhe – (Irish and Scottish) – Ancestral or nature spirit
- Sigbin (Philippine) – Goat-like vampire
- Sileni (Greek) – Bald, fat, thick-lipped, and flat-nosed followers of Dionysus
- Simargl (Slavic) – Winged dog
- Simurgh (Persian) – Dog-lion-peacock hybrid
- Singa (Batak) – Feline animal
- Sint Holo (Choctaw) – Serpentine rain spirit
- Siren (Greek) – Human-bird hybrid
- Sirin (Slavic) – Demonic human-headed bird
- Sirrush (Akkadian) – Dragon with aquiline hind legs and feline forelegs
- Sisiutl (American Indian) – Two-headed sea serpent
- Si-Te-Cah (Paiute) – Red-haired giants
- Sjörå (Norse) – Freshwater spirit
- Sjövættir (Norse) – Sea spirit
- Skin-walker (American Indian) – Animal-human shapeshifter
- Skogsrå (Scandinavian) – Forest spirit
- Sköll (Norse) – Wolf that chases the Sun
- Skookum (Chinook Jargon) – Hairy giant
- Skeleton (Medieval folklore) – Living skeletons
- Skrzak (Slavic) – Household spirit
- Sky Women (Polish) – Weather spirit
- Sleipnir (Norse) – Eight-legged horse
- Sluagh (Irish and Scottish) – Restless ghost
- Snow Lion (Tibetan) – Celestial animal
- Sodehiki-kozō (Japanese) – Invisible spirit which pulls on sleeves
- Sōgenbi (Japanese) – Fiery ghost of an oil-stealing monk
- Soragami (Japanese) – Ritual disciplinary demon
- Soraki-gaeshi (Japanese) – Sound of trees being cut down, when later none seem to have been cut
- Sorobanbōzu (Japanese) – Ghost with an abacus
- Sōtangitsune (Japanese) – Fox spirit from Kyoto
- Soucouyant (Trinidad and Tobago) – Vampiric hag who takes the form of a fireball at night
- Spearfinger (Cherokee) – Sharp-fingered hag
- Spectre (Worldwide) – Terrifying ghost
- Sphinx (Greek) – Winged woman-headed lion
- Spiriduş (Romanian) – Little people
- Spirit – Ghosts
- Spriggan (Cornish) – Guardians of graveyards and ruins
- Sprite (Medieval folklore) – little people, ghosts or elves
- Squonk (American) – Ugly and lonely creature capable of evading capture by dissolving itself into a pool of tears
- Stihi (Albanian) – Demonic dragon who guards a treasure
- Strigoi (Romanian) – Vampire
- Strix (Roman) – Vampiric bird
- Struthopodes (Medieval Bestiaries) – Humanoid whose males have enormous feet, and females have tiny feet
- Strzyga (Slavic) – Vampiric undead
- Stuhać (Slavic) – Malevolent mountain spirit
- Stymphalian Bird (Greek) – Metallic bird
- Suangi (New Guinea) – Cannibalistic sorcerer
- Succubus (Medieval folklore) – Female night-demon
- Sudice (Slavic) – Fortune spirit
- Sunakake-baba (Japanese) – Sand-throwing hag
- Sunekosuri (Japanese) – Small dog- or cat-like creature that rubs against a person's legs at night
- Surma (Finnish) – Hellhound
- Suzaku (Japanese) – Japanese version of the Chinese Vermillion Bird
- Svaðilfari (Norse) – Unnatural strong horse, father of Sleipnir
- Svartálfar (Norse) – Cavern spirits; the Black Elves
- The Swallower (Ancient Egyptian) – Crocodile-leopard-hippopotamus hybrid
- Swan maiden (Worldwide) – Swan-human shapeshifter
- Sylph (Alchemy) – Air elemental
- Sylvan (Medieval folklore) – Forest spirit
- Syrbotae (Medieval Bestiaries) – African giant
- Syrictæ (Medieval Bestiaries) – Reptilian humanoid