Protognathus

Protognathus may refer to:
 * Protognathus, genus of ground beetle described in 1950 but later considered as a synonym of Pseudognathaphanus.
 * Protognathosaurus, genus of sauropod that is originally described as Protognathus.
 * Protognathodus, genus of conodont, sometimes described as Protognathus.
 * Protognathinus, genus of extinct beetle that is sometimes misspelled as Protognathus.