Science magazines
- Short-leaved Rosemary
- Shortnose Sturgeon
- Shortnose Sucker
- Showy Indian Clover
- Sierra Nevada Bighorn Sheep
- Silene Alexandri
- Silene Hawaiiensis
- Silene Lanceolata
- Silene Perlmanii
- Siler Pincushion Cactus
- Silver Rice Rat
- Slackwater Darter
- Slender Campeloma
- Slender Chub
- Slender Orcutt Grass
- Slender Rush-pea
- Slender-billed Grackle
- Slender-horned Spineflower
- Slender-petaled Mustard
- Small Kauai Thrush