| Named By: | Edward Drinker Cope in 1869 |
| Time Period: | Late Cretaceous |
| Location: | Australia, North America and Russia |
| Size: | Around 5 meters long, but size is dependent upon species |
| Diet: | Piscivore/Carnivore |
| Fossil(s): | Many individuals |
| Classification: | | Chordata | Reptilia | Sauropterygia | Plesiosauria | Polycotylidae | Polycotylinae | |
Polycotylus is a genus of plesiosaur within the family Polycotylidae. The type species is P. latippinis and was named by American paleontologist Edward Drinker Cope in 1869. Eleven other species have been identified. The name means 'much-cupped vertebrae', referring to the shape of the vertebrae. It lived in the Western Interior Seaway of North America toward the end of the Cretaceous. One fossil preserves an adult with a single large fetus inside of it, indicating that Polycotylus gave live birth, an unusual adaptation among reptiles.