Letognathus is a genus of rhizodont tetrapodomorph that lived during the Carboniferous period. Its remains come from the Blue Beach Member of the Horton Bluff Formation, near Hantsport, Nova Scotia. Like most rhizodonts, it was of relatively large size, had a large recurved fang at the symphysis of the lower jaw, and a row of three coronoid fanks along the length of the jaw in addition to its marginal dentition. Letognathus is important for rhizodont systematics because it retains a number of primitive features, such as ossified Meckel's cartilage, are not found in the genera Rhizodus and Strepsodus.