Shellfish is a term used to describe molluscs and crustaceans used as food. Molluscs include the clam, mussel, oyster, and scallop; some crustaceans are the shrimp, lobster, crayfish, and crab. Snails, while similar to most shellfish biologically, are generally not considered to be shellfish.

Lobster and crab are considered delicacies in America, where families in the northeast region make them into the centerpiece of a summer banquet. Lobsters are generally associated with Maine and the gulf of Maine. The Chesapeake bay and Maryland generally are associated more with crabs. New England is also known for its Clam chowder, although New York and Rhode Island variants exist.

'Steamers' refers to a variety of littleneck clam (as opposed to a quahog). They are relatively small and have a white shell. The clams are put into a steamer pot and cooked for 10-15 minutes, during which the mollusks open their shells. Diners are advised never to eat a steamer that is closed, as it was most likely dead when prepared and may not be fit for consumption. Melted butter is generally a must-have for eating steamers.

In many major cities with active fishing ports, raw oyster bars are also a feature of shellfish consumption. When served freshly shucked (opened) and iced, one may find a liquid inside the shell, called the liqueur. This is a primary feature of the raw bar, and should be sampled, if not enjoyed. Oysters are thought to be an aphrodisiac.

Jewish Kosher Law traditions forbid the eating of shellfish. A rational basis taken up by some nonreligious persons is the tendency of some shellfish to feed on waste or accumulate heavy metals or toxins in their tissues. Another is that some of these dishes are consumed raw (oysters, mussles, clams and skrimp, most notably) and can make a person very ill from food poisoning.