Chrysaora melanaster, commonly known as the northern sea nettle or brown jellyfish, is a species of jellyfish native to the northern Pacific Ocean and adjacent parts of the Arctic Ocean. It is sometimes referred to as a Pacific sea nettle, but this name is also used for C. fuscescens; the name Japanese sea nettle was also used for this species, but that name now exclusively refers to C. pacifica. Although jellyfish kept in public aquariums sometimes are referred to as C. melanaster, this is the result of the historical naming confusion and these actually are C. pacifica.

The medusa of the northern sea nettle can reach 60 cm (2 ft) in diameter with tentacles growing up to 3 m (10 ft). The number of tentacles is up to 24 (three per octant). It dwells at depths of up to 100 meters, where it feeds on copepods, larvaceans, small fish, large zooplankton, and other jellies. The sting is mild, although can cause serious skin irritation and burning. The lifespan is unknown.

Habitat The northern sea nettle is found in open water of temperate northern Pacific Ocean, Arctic Ocean and especially the Bering Sea.

Ecology Pollock can be both the food of the northern sea nettle and also the competitor for potentially limited sources of prey.