The blue mussel (Mytilus edulis) is a saltwater bivalve mollusk native to the coastal North Atlantic, long harvested as food by coastal communities on both sides of the ocean. It has a deep blue-black shell up to about 10 cm long, lined in smooth, pearly white, and grows in dense clusters attached to rocks and other submerged surfaces.
Blue mussels are steamed, boiled, or sautéed; their sweet, briny meat is a staple of seafood stews, chowders, and paella, and a common simple appetizer served with bread for dipping in the cooking liquid.
Blue mussel is distinct from other commonly eaten mussel species: the Mediterranean mussel (Mytilus galloprovincialis) is milder and more common in southern Europe, while the green-lipped mussel (Perna canaliculus) is a New Zealand species with a longer, green-tinged shell. Recipes that call simply for "mussels" in North America or Europe are usually referring to blue mussel.
Blue mussels should be bought with tightly closed, undamaged shells and cooked soon after purchase; any that stay open or are cracked before cooking should be discarded.