The kelp greenling (Hexagrammos decagrammus) is a species of marine ray-finned fish belonging to the family Hexagrammidae, the greenlings. This species occurs in rocky nearshore areas of the northern Pacific especially around British Columbia and Alaska, and is common on kelp beds and on sand bottoms. They feed on crustaceans, polychaete worms, brittle stars, mollusks, and small fishes. The young are food for large predators such as lingcod and halibut. Unique to this species is its mating ritual, where males attempt to inseminate eggs in the nests of other males. This phenomenon can be explained with condition dependent mating decisions.