This list comprises 239 species of non-marine molluscs that have been recorded in the scientific literature as part of the fauna of the island of Great Britain; this total excludes species found only in hothouses and aquaria. The list includes terrestrial and aquatic gastropods, and aquatic bivalves. Molluscs that are fully marine (adapted to live in the sea) are not included here, except for two marine pulmonate snails. In other words, this list includes land snails and slugs, and freshwater and brackish water snails. It also includes freshwater mussels and clams, including some that can tolerate brackish water. Great Britain is a European island in the northeastern Atlantic, comprising the contiguous countries of England, Scotland and Wales. (Great Britain is not the same entity as the United Kingdom of Great Britain and Northern Ireland; for more information on the complex nomenclature of this area, please see terminology of the British Isles.) The mollusc fauna of the island of Ireland, which includes both the Republic of Ireland and Northern Ireland, is listed in another article: List of non-marine molluscs of Ireland. A number of species of snails listed here are sometimes also found on lists of marine species. Two listed here, in the genera Onchidella and Otina, are fully marine in habitat, but are pulmonate gastropods that breathe air at low tide rather than having gills like most marine species. Other species listed here live in habitats that are intermediate between land and saltwater, or in brackish water habitats intermediate between freshwater and full-salinity saltwater. Additional species are still being added to the list of the non-marine malacofauna of Great Britain. Four of the more recent discoveries are: Papillifera papillaris, first recorded in 1993 but probably the result of introductions with Italian statuary a century or more earlier; Selenochlamys ysbryda, a species new to science, which was first found in 2004; Candidula olisippensis, discovered on a Cornish cliff in 2011; and Monacha ocellata, found near Tilbury docks in 2017. Other species have been added to the list as a result of taxonomic revisions; for instance, only in 2009 was it recognised that snails previously known as Pupilla muscorum constituted two sibling species occupying different habitats, with both Pupilla muscorum sensu stricto and Pupilla alpicola occurring in Britain. A major revision of the slug fauna published in 2014, partly based on genetic sequencing, established that there were 20% more species than had previously been recognised. Not all these species have been definitely identified and some are formally undescribed. In addition to the species that survive outdoors in Great Britain, there are also another 15 exotic gastropod species (some terrestrial and some aquatic) which live as "uninvited guests" in greenhouses and their enclosed aquaria. These species are known as "hothouse aliens", and are listed separately at the end of the main list. In this list these species are not counted as part of the fauna. Also not included are species such as Eobania vermiculata and Milax nigricans that have been found outdoors on single occasions but seem never to have established persisting populations. The following table shows a summary of species numbers.

Conservation

Those species that are recognized as endangered are shown with an E after their name, see List of endangered species in the British Isles. Some species are protected in the United Kingdom under the Wildlife and Countryside Act 1981: Two of the land snails on the list (Fruticicola fruticum and Cernuella neglecta) are now locally extinct (in Great Britain, sometimes abbreviated here as G.B.), but they still occur in other parts of Europe.

Systematic list

The list is arranged by presumed biological affinity, rather than being alphabetical by family. A number of species are listed with subspecies, in cases where there are well-recognized subspecies in different parts of Europe. For some species a synonym is given, where the species may perhaps be better known under another name. An attempt has been made to label the families as aquatic, terrestrial or intermediate, and an indication is given where it is thought that the species is introduced. Some introductions to Great Britain are quite ancient, dating from Roman times or even earlier. Those species that do not have a shell usually do not leave an archeological or fossil record, and therefore it is not always possible to determine whether they are native or introduced. Species are considered to be native, unless otherwise indicated on the list; this information is taken from Kerney (1999) updated in the case of slugs with the opinions of Rowson et al. (2014). The status and taxonomy of freshwater gastropods has been updated according to Rowson et al. (2021). Note: the images used to illustrate the list are mostly of specimens that were found in other countries.

Gastropoda

The following gastropods are pulmonates:

Bivalvia

List of "hothouse alien" species

This group of exotic land and freshwater species are not truly part of the fauna because they do not live in the wild. Many are tropical and thus are incapable of surviving in the wild in Great Britain; instead they have established themselves as uninvited inhabitants of greenhouses, aquaria within greenhouses, and similar artificially-heated habitats.