Cornu aspersum, known by the common name garden snail, is a species of land snail. As such it is a terrestrial pulmonate gastropod mollusc in the family Helicidae, which include the most commonly familiar land snails. Of all terrestrial molluscs, this species may well be the most widely known. In English texts it was classified under the name Helix aspersa for over two centuries, but the prevailing classification now places it in the genus Cornu.
The adult bears a hard, thin calcareous shell 25–40 mm in diameter and 25–35 mm high, with four or five whorls. The shell is variable in color and shade but generally is dark brown, brownish golden, or chestnut with yellow stripes, flecks, or streaks (characteristically interrupted brown colour bands). The aperture is large and characteristically oblique, its margin in adults is white and reflected.
The body is soft and slimy, brownish-grey, and the animal retracts itself entirely into the shell when inactive or threatened. When injured or badly irritated the animal produces a defensive froth of mucus that might repel some enemies or overwhelm aggressive small ants or the like. It has no operculum; during dry or cold weather it seals the aperture of the shell with a thin membrane of dried mucus; the term for such a membrane is epiphragm. The epiphragm helps the snail retain moisture and protects it from small predators such as some ants.
Like other Pulmonata, Cornu aspersum is a hermaphrodite, producing both male and female gametes. Reproduction is usually sexual, although self-fertilisation sometimes occurs. During a mating session of several hours, two snails exchange sperm. Cornu aspersum is one of the species that uses love darts during mating.
About two weeks after fertilisation, the snail lays a batch of about 80 spherical pearly-white eggs into crevices in the topsoil or sheltered under stones or the like. In a year it may lay six batches or so. The size of the egg is 4 mm.
The young snails take one to two years to reach maturity. In some regions snail farms produce them commercially.