Pliosauridae is a family of plesiosaurian marine reptiles from the Latest Triassic to the early Late Cretaceous (Rhaetian to Turonian stages).

The family is more inclusive than the archetypal short-necked large headed species that are placed in the subclade Thalassophonea, with early, primitive forms resembling other plesiosaurs with long necks.

Thalassophonean pliosaurs represented the largest marine predators during their existence, spanning more than 80 million years.

[2] Pliosauridae is a stem-based taxon defined in 2010 (and in earlier studies in a similar manner) as "all taxa more closely related to Pliosaurus brachydeirus than to Leptocleidus superstes, Polycotylus latipinnis or Meyerasaurus victor".

It is a stem-based taxon defined as "all taxa more closely related to Pliosaurus brachydeirus than to Marmornectes candrewi".