| Named By: | William Daniel Conybeare in 1822 (Gideon Mantell added the species name in in 1829) |
| Time Period: | Late Cretaceous, 70 Ma |
| Location: | Western Europe and North America, quite probably even further afield |
| Size: | Largest individuals from 15 to potentially up to 18 meters long |
| Diet: | Carnivore |
| Fossil(s): | Many specimens |
| Classification: | | Chordata | Reptilia | Mosasauridae | Mosasaurini | |
| Also known as: | | Amphekepubis | Baseodon | Batrachiosaurus | Batrachotherium | Capelliniosuchus | Drepanodon | Lesticodus | Nectoportheus | Mosasaurus fulciatus | Mosasaurus oarthrus | Mosasaurus | maximus | Mosasaurus princeps | Pterycollosaurus | |
Mosasaurus ("lizard of the Meuse River") is a genus of mosasaurs, extinct carnivorous aquatic lizards. It existed during the Maastrichtian age of the late Cretaceous period, between about 70 and 66 million years ago, in western Europe and North America. The name means "Meuse lizard", as the first specimen was found near the Meuse River (Latin Mosa + Greek sauros lizard).