Crotalus enyo is a venomous pitviper species native to the coast and islands of northwestern Mexico. Three subspecies are currently recognized, including the nominate subspecies described here. The maximum reported length of this species is 89.8 cm. It is sexually dimorphic, with the males typically being larger than the females. The head is remarkably small and narrow, while the eyes are proportionately large. Found in western Mexico. In the north it is found in the Baja California Peninsula from around Río San Telmo on the west coast and from opposite Isla Angel de la Guarda on the gulf coast, south to Cabo San Lucas.