The superorder Peracarida is a large group of malacostracan crustaceans, having members in marine, freshwater, and terrestrial habitats.

They are chiefly defined by the presence of a brood pouch, or marsupium, formed from thin flattened plates (oostegites) borne on the basalmost segments of the legs.

This brood pouch is enclosed by the large, flexible oostergites, bristly flaps which extend from the basal segments of the thoracic appendages, which form the floor of a chamber roofed by the animal's sternum.

[3] Other characteristics include the possession of a single pair of maxillipeds (rarely 2–3), of mandibles with an articulated accessory process between the molar and incisor teeth in the adults (called the lacinia mobilis), and of a carapace which is often reduced in size and is not fused with the posterior thoracic somites.

The World Register of Marine Species WoRMS (2023) includes the following 13 orders:[6] Of these Bochusacea, Ingolfiellida and Stygiomysida have been added since the classification of Martin & Davies (2001).