Ornithostoma (meaning "bird mouth") is a genus of pterodactyloid pterosaur that lived during the Early Cretaceous period (Albian stage) of Europe, around 110 million years ago.

Ornithostoma was once thought to have been a senior synonym of the pteranodontid Pteranodon due to its toothless anatomy and prior naming.

[4] In 1891 however, he named the type species Ornithostoma sedgwicki Seeley 1891, apart from the snout fragments also referring to pelvis elements, claiming it was identical to Pteranodon and had priority.

[8] In a 1994 paper, S. Christopher Bennett like Lydekker considered Ornithostoma to be distinct from Pteranodon, mainly because of the lower edge ridges of the jaw.

[10] In 2012, Alexander O. Averianov again recombined the holotype with CAMSM B.54406 and selected postcrania, the combination showing traits that indicated a position in the Azhdarchoidea, representing an animal similar in some ways to Tapejara.

In 1914 Nikolai Nikolaevich Bogolubov named a single large vertebra found near Petrovsk Ornithostoma orientalis.