Sea snails are slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone.
They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the absence of a visible shell.
Because the shells of sea snails are strong and durable in many cases, as a group they are well represented in the fossil record.
A number of species of sea snails are harvested in aquaculture and used by humans for food, including abalone, conch, limpets, whelks (such as the North American Busycon species and the North Atlantic Buccinum undatum) and periwinkles including Littorina littorea.
The shells of a few species of large sea snails within the Vetigastropoda have a thick layer of nacre and have been used as a source of mother of pearl.