Crotalus is a genus of venomous pit vipers in the family Viperidae, known as rattlesnakes or rattlers. The genus is found only in the Americas from southern Canada to northern Argentina, and member species are colloquially known as rattlesnakes. The generic name Crotalus is derived from the Greek word κρόταλον krótalοn, which means "rattle" or "castanet", and refers to the rattle on the end of the tail, which makes this group so distinctive. Currently, 32 to 45 species are recognized as being valid.
The genus Crotalus is found in the Americas from southern Canada to central Argentina.