A medium-sized edible mussel, Mytilus edulis, found on the North Atlantic coast of North America, Europe, and in other temperate and polar waters around the world.
A saltwater mussel, usually edible, of the order Mytilida in subclass Pteriomorphia.
A freshwater mussel, usually edible, of the order Unionida in subclass Palaeoheterodonta.
Any of certain other bivalves of somewhat similar appearance, such as the zebra mussel and quagga mussel of the family Dreissenidae in subclass Heterodonta.