Mysis diluviana is a mysid crustacean (opossum shrimp) found in freshwater lakes of northern North America.

It has two pairs of relatively long antennae, associated with rounded antennal plates; large, stalked compound eyes; the thorax covered by a coat-like carapace; a muscular, cylindrical abdomen; and a tail fan featuring a telson with a V-shaped terminal cleft.

Recently, however, another invasive mysid of European origin, Hemimysis anomala, has rapidly spread in the Great Lakes.

[3] The native mysids in freshwater lakes of the Canadian Arctic and in coastal lagoons of Alaska belong to another, closely related species, Mysis segerstralei.

[4][5] Mysis diluviana is found in deep, cold oligotrophic lakes with high levels of dissolved oxygen, where it stays mainly below the thermocline.