Mysis relicta is a shrimp-like crustacean in the Mysida order, native to lakes of Northern Europe and to the brackish Baltic Sea.

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.

The distribution of Mysis relicta is restricted to previously glaciated regions in Northern Europe, including northwest Russia, Finland, Denmark,[1] Sweden, southeast Norway, and parts of Germany, Poland, and Lithuania.

In the Baltic Sea, M. relicta is only found in the most diluted marginal parts of the basin, where it also stays in deeper water.

A current active area of research is the effect of mysid reintroduction on lake food webs after acidification.