Science magazines
- Comanche Springs Pupfish
- Conasauga Logperch
- Concho Water Snake
- Conejo Dudleya
- Conservancy Fairy Shrimp
- Contra Costa Goldfields
- Contra Costa Wallflower
- Cook's Holly
- Cooke's Koki'o
- Cooley's Meadowrue
- Cooley's Water-willow
- Coosa Moccasinshell
- Copperbelly Water Snake
- Cordia Bellonis
- Coyote Ceanothus
- Cracking Pearlymussel
- Cranichis Ricartii
- Crenulate Lead-plant
- Crested Honeycreeper
- Cuatro Cienegas Softshell Turtle