Prognathodon is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like Mosasaurus and Clidastes. Prognathodon has been recovered from deposits ranging in age from the Campanian to the Maastrichtian in the Middle East, Europe and North America. Prognathodon means "forejaw tooth.
Prognathodon constitutes one of the largest-bodied mosasaur genera, with the largest known skull exceeding 140 cm in length. Despite its massive size, remains of the genus are often fragmentary and incomplete. To date, very few specimens are known with articulated skulls and none with an entire skeleton. Though many species were large with sizes approaching or potentially exceeding 10 meters, such as P. currii, P. saturator and P.overtoni.
Prognathodon was first described by Louis Dollo in 1889 based on specimens gathered in Belgium.