Acanthognathus (Greek: ákantha = thorn, gnáthos = jaw) is a genus of ants that are found in tropical Central and South America.

Acanthognathus has large, line-shaped jaws, each with an apical fork of 3 spiniform teeth that interlock when fully closed; Preapical dentition sometimes present but often absent.

The genus was established by Mayr (1887) to house the species A. ocellatus, described from a single worker found in Brazil.

[4] Mistakenly, the name Acanthognathus was re-used by German ichthyologist G. Duncker in 1912 for a genus of syngnathid fish,[5] but that is invalid as it is a junior homonym.

[7][8] To further confuse, a genus of nemesiid spiders, Acanthogonatus, is frequently misspelled Acanthognathus.