The Mygalomorphae, previously called the Orthognatha, are a suborder of spiders. The latter name comes from the orientation of the fangs which point straight down and do not cross each other (cf araneomorph). This suborder includes the heavy bodied, stout legged spiders popularly known as tarantulas. They have ample poison glands that lie entirely within their chelicerae. Their chelicerae and fangs are large and powerful. Occasionally members of this suborder will even kill small fish, small mammals, etc. Most members of this suborder occur in the tropics and subtropics, but their range can extend farther north, e.g. into the southern and western regions of the United States.

This Sphodros rufines shows the essentially vertical orientation of the chelicerae and fangs.

These spiders should be distinguished from their namesake, the Italian tarantula (Lycosa tarantula), which is one of the wolf spiders.