Metlapilcoatlus occiduus is a pit viper subspecies[4] endemic to southern Mexico, Guatemala, and El Salvador.

The largest specimens reported are a male of 74.8 cm (29+1⁄2 in) from Baja Verapaz, Guatemala, and a female of 79.5 cm (31+1⁄4 in) from Volcán de Agua, Escuintla, Guatemala.

[3] The type locality given is "Saint-Augustín (Guatemala), versant occidentale de la Córdillère.

[2] Its habitat includes subtropical wet forest on the Pacific versant from southeastern Chiapas, Mexico to western El Salvador.

Regarded as a full species, Metlapilcoatlus occiduus, by Campbell and Lamar (2004).