Science magazines
- Small Whorled Pogonia
- Small's Milkpea
- Small-anthered Bittercress
- Smith's Blue Butterfly
- Smoky Madtom
- Smooth Coneflower
- Snake River Physa Snail
- Snakeroot
- Sneed Pincushion Cactus
- Sockeye Salmon
- Socorro Isopod
- Socorro Springsnail
- Soft Bird's-beak
- Soft-leaved Indian Paintbrush
- Solano Grass
- Sonoma Alopecurus
- Sonoma Spineflower
- Sonoma Sunshine
- Sonora Chub
- Sonora Tiger Salamander