Gastrophryne, the narrowmouth toads (also American narrowmouth toads, North American narrow-mouthed toads), is a genus of microhylid frogs found in the Americas between Honduras and southern United States.

[1] Its name means ‘belly-toad’, referring to its large belly, from the Ancient Greek gastēr (γαστήρ, ‘belly, stomach’) and phrunē (φρύνη, ‘toad’).

[2] Gastrophryne is closely related to Hypopachus.

Some species that were earlier placed in Gastrophryne were more closely related to Hypopachus, rendering the genus paraphyletic.

[3] Gastrophryne frogs were the first species to be recognized to be experiencing speciation by reinforcement[4] and lead to the coining of the term reinforcement by W. Frank Blair in 1955;[5] a concept proposed by Theodosius Dobzhansky decades earlier.