Crotalus simus is a venomous pit viper species found in Mexico and Central America.

The specific epithet is Latin for "flat-nosed", likely because its head is blunt compared with lanceheads (Bothrops).

Local symptoms may be severe, with pain, massive swelling, blistering, and necrosis that lead to fasciotomies and in some cases amputations.

Systemic effects involving hemostatic disturbances are rare, as are kidney failure, and neurotoxicity.

[3] Molecular genetic data suggest the taxa culminatus and tzabcan should be considered as separate species from C. simus[7]