C. cyaneus

C. cyaneus may refer to:
 * Ceanothus cyaneus, the San Diego buckbrush or lakeside ceanothus, a flowering plant species found in California and Baja California
 * Circus cyaneus, the hen harrier, a bird of prey species that breeds in Eurasia
 * Copadichromis cyaneus, a fish species found in Malawi, Mozambique and Tanzania