Crotalus cerastes, known as the sidewinder, horned rattlesnake or sidewinder rattlesnake, is a pit viper species belonging to the genus Crotalus, and is found in the desert regions of the Southwestern United States and northwestern Mexico. Like all other pit vipers, it is venomous. Three subspecies are currently recognized.

The Crotalinae, commonly known as pit vipers, or pit adders, are a subfamily of vipers found in Asia and the Americas. Like all other vipers, they are venomous. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on both sides of the head. Currently, 23 genera and 155 species are recognized: These are also the only viperids found in the Americas. The groups of snakes represented here include rattlesnakes, lanceheads, and Asian pit vipers. The type genus for this subfamily is Crotalus, of which the type species is the timber rattlesnake, C. horridus.