Clausilia dubia is a species of small, very elongate, left-handed air-breathing land snail, a sinistral terrestrial pulmonate gastropod mollusk in the family Clausiliidae, the door snails, all of which have a clausilium.

[2] The species is widespread in Europe, living in countries and islands including (among others):[1] All the species of snails in the family of door snails are left-handed, which is an uncommon feature in gastropods in general.

These snails have shells which are extremely high-spired, with numerous whorls.

Clausilia dubia is a relatively large species for this family, reaching 16 mm in height.

The weight of the adult live snail is about 123 mg.[4]