Clausiliidae, also known by the common name door snails, is a taxonomic family of small, very elongate, mostly left-handed, air-breathing land snails, sinistral terrestrial pulmonate gastropod mollusks.

With over 1700 recognized recent and fossil species, this is among the most diverse families of terrestrial gastropods (cf. Orthalicidae), although the marine gastropod family Pyramidellidae is larger.

Most species of Clausiliidae have an anatomical structure known as a clausilium, which enables the snail to close off the aperture of the shell with a sliding "door".

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