The Pliosauroidea, meaning "lizards beyond the ordinary", is a genus of marine reptiles that lived during the middle and late Jurassic and early Cretaceous periods of the Mesozoic era. The Pliosauria belongs to the Plesiosauria order, which originally included only the Pliosauridae, but now includes other families and genera. Pliosaurs are the branch of all finned saurians with the strongest bite and combat power, and even became a rising star. When they existed, their ecological niche even surpassed that of the more marine ichthyosaurs. Pliosaurs and their close relatives, the true plesiosaurs, and the entire finned superorder were not dinosaurs.

Compared to the "long-necked" plesiosaurs, pliosaurs are characterized by "short necks, long heads, and moderately fast movements but extremely fierce." Pliosaurs are carnivorous animals with long, strong jaws with multiple rows of sharp teeth, suitable for catching small, large prey. The huge head is mostly a mouth, with huge eyes and a pair of nostrils, which can directly smell water, just like other plesiosaurs. Like other plesiosaurs, they swam using four large flippers that had evolved into long, wide, strong flippers at the corners of their long bodies. Their tails were short and tapering, probably used as rudders, as in other plesiosaurs. They were probably well adapted to the deep sea. Pliosaurs ranged from 4 to 15 meters in length. They probably preyed on ichthyosaurs or other plesiosaurs.