Lusognathus (meaning "Lusitanian jaw") is an extinct genus of gnathosaurine pterosaurs from the Late Jurassic Lourinhã Formation of Portugal.

The genus contains a single species, Lusognathus almadrava, known from a parts of the upper jaw, teeth, and cervical vertebrae.

The specimen consists of an incomplete premaxillary rostrum, a fragment of the maxillae, two isolated partial teeth, and three or four fragmentary cervical vertebrae.

[1] In 2023, Alexandra E. Fernandes, Victor Beccari, Alexander Wilhelm Armin Kellner and Octávio Mateus described Lusognathus almadrava as a new genus and species of ctenochasmatid pterosaur based on these fossil remains.

Such a considerable size is confirmed by pterosaur tracks found ten kilometres to the south showing foot lengths of between 5.5–15 centimetres (2.2–5.9 in).

The teeth are very robust and large; the fourth tooth has a crown length 23.5 millimetres (0.93 in) longer than half of the transverse snout width at this point.

[1] Fernandes et al. (2023) recovered Lusognathus as a member of the ctenochasmatid clade Gnathosaurinae, as the sister taxon to the two known species of Gnathosaurus, G. subulatus and G. macrurus.

The results of their phylogenetic analyses are shown in the cladogram below:[1] "Pterodactylus" micronyx Ctenochasma elegans Liaodactylus Pterodaustro Gegepterus Beipiaopterus Kepodactylus Elanodactylus Feilongus Moganopterus Ardeadactylus Huanhepterus Plataleorhynchus Lusognathus Gnathosaurus spp.