S
- Sacalia bealei — Beal's-eyed Turtle
- Sacalia quadriocellata — Four-eyed Turtle
- Saguinus bicolor — Brazilian Bare-faced Tamarin, Pied Bare-faced Tamarin, Pied Tamarin
- Saguinus oedipus — Cotton-headed Tamarin, Cottontop Tamarin
- Saiga tatarica — Saiga Antelope, Saiga
- Saimiri oerstedii — Black-crowned Central American Squirrel Monkey, Central American Squirrel Monkey, Red-backed Squirrel Monkey
- Sarcophilus harrisii - Tasmanian Devil
- Salaria economidisi
- Salmo carpio
- Salmo peristericus
- Salmo platycephalus — Ala balik
- Salmothymus obtusirostris — Adriatic salmon
- Salvelinus japonicus — Kirikuchi char
- Samoana abbreviata — Short Samoan tree snail
- Samoana annectens
- Samoana attenuata
- Samoana conica
- Samoana diaphana — Moorean viviparous tree snail
- Samoana fragilis — Tree snail
- Samoana solitaria — Moorean viviparous tree snail
- Samoana thurstoni
- Sandelia bainsii — Eastern Province Rocky
- Santa Catalina Island Shrew
- Sarotherodon caroli — Fissi
- Sarotherodon linnellii — Unga
- Sarotherodon lohbergeri — Leka keppe
- Sarotherodon steinbachi — Kululu
- Sarothrura ayresi — White-winged Flufftail
- Sarothrura watersi — Slender-billed Flufftail
- Saxicola dacotiae — Fuerteventura Chat
- Scaphiophryne boribory
- Scaphiophryne gottlebei
- Scaphirhynchus albus — Pallid sturgeon
- Scaphirhynchus suttkusi — Alabama sturgeon
- Scardinius graecus — Greek Rudd
- Scardinius scardafa
- Scaturiginichthys vermeilipinnis — Red-finned blue-eye
- Schayera baiulus
- Schizoeaca perijana — Perijá Thistletail
- Schizothorax lepidothorax
- Scinax alcatraz
- Scleropages formosus — Asian arowana, Asian bonytongue, Gold arowana, Golden Dragon Fish, Kelesa
- Scolomys melanops — South American Spiny Mouse
- Scolomys ucayalensis — Ucayali Spiny Mouse
- Scolopax rochussenii — Moluccan Woodcock
- Scomberomorus concolor — Monterrey Spanish mackerel
- Scotonycteris ophiodon — Pohle's Fruit Bat
- Scotopelia ussheri — Rufous Fishing-owl
- Scotophilus borbonicus — Lesser Yellow Bat
- Scutiger chintingensis
- Scutiger maculatus
- Scutiger muliensis
- Scutiger ningshanensis
- Scutiger pingwuensis
- Scytalopus iraiensis — Marsh Tapaculo
- Scytalopus psychopompus — Bahia Tapaculo
- Sebastes fasciatus — Redfish
- Sebastes paucispinus — Bocaccio rockfish
- Sebastolobus alascanus — Shortspine thornyhead
- Selevinia betpakdalaensis — Desert Dormouse
- Sephanoides fernandensis — Juan Fernández Firecrown
- Serinus flavigula — Yellow-throated Seedeater
- Sheppardia gabela — Gabela Akalat
- Sheppardia montana — Usambara Akalat
- Sicista armenica — Armenian Birch Mouse
- Sicista caudata — Long-tailed Birch Mouse
- Sigmodontomys aphrastus — Harris's Rice Water Rat
- Silurus mento
- Simias concolor — Pig-tailed Langur, Pig-tailed Snub-nosed Monkey
- Sinhalestes orientalis
- Siphonaria compressa
- Siphonorhis americana — Jamaican Pauraque
- Sitta ledanti — Algerian Nuthatch
- Sitta victoriae — White-browed Nuthatch
- Smilisca dentata — Rana-de Arbol De Tierras Altas
- Sminthopsis aitkeni — Kangaroo Island Dunnart
- Sminthopsis douglasi — Julia Creek Dunnart
- Sminthopsis psammophila — Large Desert Marsupial-mouse, Sandhill Dunnart, Sandhill Sminthopsis
- Solenodon cubanus — Almiqui, Cuban Solenodon
- Solenodon paradoxus — Haitian Solenodon, Hispaniolan Solenodon
- Solisorex pearsoni — Pearson's Long-clawed Shrew
- Solomys ponceleti — Poncelet's Giant Rat, Poncelet's Naked-tailed Rat
- Somatochlora hineana — Hine's Emerald
- Somatogyrus biangulatus — Angular pebblesnail
- Somatogyrus coosaensis — Coosa pebblesnail
- Somatogyrus crassus — Stocky pebblesnail
- Somatogyrus currierianus — Tennessee pebblesnail
- Somatogyrus decipiens — Hidden pebblesnail
- Somatogyrus excavatus — Ovate pebblesnail
- Somatogyrus hendersoni — Fluted pebblesnail
- Somatogyrus humerosus — Atlas pebblesnail
- Somatogyrus nanus — Dwarf pebblesnail
- Somatogyrus obtusus — Moom pebblesnail
- Somatogyrus pygmaeus — Pygmy pebblesnail
- Somatogyrus quadratus — Quadrate pebblesnail
- Somatogyrus strengi — Rolling pebblesnail
- Somatogyrus tennesseensis — Opaque pebblesnail
- Somatogyrus virginicus — Panhandle pebblesnail
- Somersiella sterreri
- Somuncuria somuncurensis — Somuncura Frog
- Sorex cansulus — Gansu Shrew
- Sorex cylindricauda — Greater Stripe-backed Shrew, Stripe-backed Shrew
- Sorex hydrodromus — Pribilof Island Shrew
- Sorex jacksoni — St Lawrence Island Shrew
- Sorex kozlovi — Kozlov's Shrew
- Sorex sadonis — Sado Shrew
- Sorex sclateri — Sclater's Shrew
- Sorex stizodon — San Cristobal Shrew
- Soriculus salenskii — Salenski's Shrew
- Spelaeoecia bermudensis
- Spelaeorchestia koloana — Kaui Cave Amphipod
- Speleoithona bermudensis
- Speleomantes supramontis — Supramonte Cave Salamander
- Speleoperipatus spelaeus
- Speleophria bivexilla
- Speleophria scottodicarloi
- Speocirolana thermydromis
- Speoplatyrhinus poulsoni — Alabama cavefish
- Spermophilus brunneus — Idaho Ground Squirrel
- Sphaerodactylus micropithecus — Monito Gecko
- Sphaerolana affinis
- Sphaerolana interstitialis
- Spheniscus mendiculus — Galápagos Penguin
- Spilocuscus rufoniger — Black-spotted Cuscus
- Spiralothelphusa fernandoi
- Spiralothelphusa parvula
- Spizaetus bartelsi — Javan Hawk-eagle
- Spizaetus floris — Flores Hawk-eagle
- Spizella wortheni — Worthen's Sparrow
- Spizocorys fringillaris — Botha's Lark
- Sporophila melanops — Hooded Seedeater
- Sporophila palustris — Marsh Seedeater
- Sporophila zelichi — Entre Ríos Seedeater
- Spratellicypris palata — Palata
- Squalius anatolicus
- Squalius keadicus
- Squalius lucumonis
- Squalius microlepis
- Squalius palaciosi — Bogardilla
- Squalius torgalensis
- Squatina aculeata — Monkfish, Sawback angelshark, Spiny angelshark
- Squatina argentina — Argentine angelshark, Longfin Angel Shark
- Squatina occulta — Smoothback angel shark
- Squatina oculata — Monkfish, Smoothback angel shark
- Squatina squatina — Angel shark
- Stachyris nigrorum — Negros Striped-babbler
- Stagnicola utahensis — Thickshell pondsnail
- Stanleya neritinoides
- Starnoenas cyanocephala — Blue-headed Quail-dove
- Stenomys vandeuseni — Van Deusen's Rat
- Stephopaedes anotis — Chirinda Toad
- Stephopaedes howelli
- Stephopaedes usambarae
- Stereolepis gigas — Black sea bass, Giant sea bass
- Sterna albostriata — Black-fronted Tern
- Sterna bernsteini — Chinese Crested-tern
- Sterna lorata — Peruvian Tern
- Stomatepia mariae — Nsess
- Stomatepia mongo — Mongo
- Stomatepia pindu — Pindu
- Streptocephalus dendrophorus
- Streptocephalus dendyi
- Streptocephalus gracilis
- Streptocephalus guzmani
- Streptocephalus moorei
- Streptocephalus woottoni — Riverside Fairy Shrimp
- Streptocephalus zuluensis
- Strigops habroptila — Kakapo
- Stumpffia helenae
- Sturnira thomasi — Thomas's Yellow-shouldered Bat
- Sturnus melanopterus — Black-winged Starling
- Stygobromus hayi — Hay's Spring Amphipod
- Stygobromus pecki — Peck's Cave Amphipod
- Stymphalornis acutirostris — Marsh Antwren
- Subuliniscus arambourgi
- Succinea piratarum
- Succinea quadrasi
- Suncus ater — Black Shrew
- Suncus fellowesgordoni — Sri Lanka Shrew
- Suncus mertensi — Flores Shrew
- Suncus zeylanicus — Jungle Shrew
- Sundamys maxi — Bartels's Rat
- Sundasciurus juvencus — Northern Palawan Tree Squirrel
- Sus cebifrons — Visayan Warty Pig
- Sus salvanius — Pygmy Hog
- Sus verrucosus — Javan Pig, Javan Warty Pig
- Sylvilagus dicei — Dice's Cottontail
- Sylvilagus graysoni — Tres Marias Cottontail, Tres Marias Rabbit
- Sylvilagus insonus — Omilteme Cottontail, Omilteme Rabbit
- Sylvisorex camerunensis
- Sylvisorex isabellae — Isabella Shrew
- Sympetrum nigrifemur
- Synallaxis infuscata — Plain Spinetail
- Synallaxis tithys — Blackish-headed Spinetail
- Synallaxis zimmeri — Russet-bellied Spinetail
- Syncaris pacifica — California freshwater shrimp
- Syngnathus watermeyeri — River pipefish
- Sypheotides indicus — Lesser Florican
Read more about this topic: IUCN Red List Endangered Animal Species