The black-tailed rattlesnake is a venomous pit viper species found in the southwestern United States and Mexico. Four subspecies are currently recognized, including the nominate subspecies described here.

Crotalus is a genus of venomous pit vipers, commonly known as rattlesnakes or rattlers, in the family Viperidae. The genus is found only in the Americas from southern Canada to northern Argentina. 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. As of July 2023, 44 to 53 species are recognized as valid.