| Named By: | Charles Lewis Camp in 1951 (originally described in 1942, but under the name Kolposaurus) |
| Time Period: | Late Cretaceous, 70 Ma |
| Location: | USA - California - Moreno Formation |
| Size: | Body around 9 meters long with a 39 centimetre skull for P. bennisoni, and a body up to 13 meters long with a 59 centimetre skull for P. tuckeri |
| Diet: | Carnivore/Piscivore |
| Fossil(s): | Remains of at least a few individuals as well as skin impressions |
| Classification: | | Chordata | Reptilia | Squamata | Mosasauridae | Mosasaurinae | |
| Also known as: | | Garzasaurus | Plotosaurus tuckeri | |
Plotosaurus ("swimmer lizard") is an extinct genus of mosasaur from the Upper Cretaceous (Maastrichtian) of Fresno County, California. Originally named Kolposaurus (meaning "bay lizard") by Berkeley paleontologist Charles Lewis Camp in 1942, it was changed to Plotosaurus in 1951 when Camp discovered the name had already been assigned to a type of nothosaur.