Microcleididae is an extinct family of basal plesiosauroid plesiosaurs from the Early Jurassic (middle Sinemurian to late Toarcian stages) of France, Germany, Portugal and the United Kingdom.

Ketchum and Benson (2010) found the traditional "microcleidid" genera to nest within a monophyletic Plesiosauridae, in a close position to Plesiosaurus.

[1] To avoid further confusion between Plesiosauridae and Microcleididae, Benson et al. (2012) proposed a stem-based definition for this taxon, utilizing Plesiosaurus as an external specifier.

Microcleididae was defined as "Microcleidus homalospondylus and all taxa more closely related to it than to Plesiosaurus dolichodeirus, Cryptoclidus eurymerus, Elasmosaurus platyurus, Leptocleidus superstes, Pliosaurus brachydeirus or Polycotylus latipinnis."

Benson et al. (2012) found strong support for Microcleididae, however their diagnosis focused on unambiguous postcranial synapomorphies since cranial material of basal microcleidids is unknown.