Science magazines
- Clay Reed-mustard
- Clay's Hibiscus
- Clay-loving Wild-buckwheat
- Clear Creek Gambusia
- Clover Lupine
- Clover Valley Speckled Dace
- Clubshell
- Coachella Valley Fringe-toed Lizard
- Coachella Valley Milk-vetch
- Coastal California Gnatcatcher
- Coastal Dunes Milk-vetch
- Cobana Negra
- Cochise Pincushion Cactus
- Coffin Cave Mold Beetle
- Coho Salmon
- Colorado Pikeminnow
- Columbian White-tailed Deer
- Colusa Grass
- Comal Springs Dryopid Beetle
- Comal Springs Riffle Beetle