Leptocleidus is a genus of plesiosaur in the family Leptocleididae. It originally lived from the Valanginian to Barremian ages of the early Cretaceous period, from 140 to 125 million years ago, with fossils found widely in the Eastern Hemisphere. There are three recognized species: the type species Leptocleidus superstes from England, Leptocleidus clemai from western Australia, and Leptocleidus capensis from South Africa.
