Hydrobiidae, commonly known as mud snails, is a large cosmopolitan family of very small freshwater and brackish water snails with an operculum; they are in the order Littorinimorpha.

Alzoniella is a genus of minute freshwater spring snails, aquatic gastropod mollusks or micromollusks in the family Hydrobiidae.

Alzoniella slovenica is a species of very small or minute freshwater snail with an operculum, an aquatic gastropod mollusk in the family Hydrobiidae, which are sometimes known as the snouted water snails.

Amnicola limosus, common name the mud amnicola, is a species of very small aquatic snail, an operculate gastropod mollusk in the family Hydrobiidae.
Belgrandiella is a genus of minute freshwater snails with a gill and an operculum, aquatic gastropod mollusks in the family Hydrobiidae.

Belgrandiella parreyssi is a species of minute freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Hydrobiidae. This species is endemic to Austria where it is found only in one thermal spring at Bad Voeslau, south of Vienna. Due to man made changes of the habitat the population has been decreasing rapidly since the 1970s.
Belgrandiella wawrai is a species of minute freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Hydrobiidae. This species is endemic to Austria.

Ecrobia truncata, common name the truncated marsh hydrobia or minute hydrobia, is a species of very small aquatic snail, an operculate gastropod mollusk in the family Hydrobiidae.

Graecoanatolica is a genus of small freshwater snails, aquatic gastropod mollusks in the family Hydrobiidae.

Graecoanatolica macedonica is an extinct species of small freshwater snail, an aquatic gastropod mollusk in the family Hydrobiidae.
Graziana is a genus of minute freshwater snails with an operculum, aquatic gastropod molluscs or micromolluscs in the family Hydrobiidae.

Hauffenia is a genus of minute freshwater snails with an operculum, aquatic gastropod molluscs or micromolluscs in the family Hydrobiidae.

Hauffenia sp. nov. is an as yet undescribed species of freshwater snail that lives underground, an aquatic gastropod mollusk in the family Hydrobiidae. This species is found in Slovakia.

Hydrobia is a genus of very small brackish water snails with a gill and an operculum, aquatic gastropod mollusks in the family Hydrobiidae.

Hydrobia acuta is a species of very small (4-6mm.) brackish water snail with a gill and an operculum, an aquatic gastropod mollusk in the family Hydrobiidae.

Islamia is a genus of small freshwater snails with a gill and an operculum, aquatic gastropod mollusks in the family Hydrobiidae.

Littoridinops is a genus of very small aquatic snails, operculate gastropod mollusks in the family Hydrobiidae.

Littoridinops monroensis is a species of very small aquatic snail, an operculate gastropod mollusk in the family Hydrobiidae.

Marstonia is a genus of freshwater snails with a gill and an operculum, aquatic gastropod mollusks in the family Hydrobiidae.

Marstonia comalensis is a species of minute freshwater snail with a gill and an operculum, an aquatic gastropod mollusk or micromollusk in the family Hydrobiidae. It is found in south central Texas, United States.

Marstonia scalariformis, previously known as Pyrgulopsis scalariformis, common name the moss pyrg, is a species of freshwater snail with a gill and an operculum, aquatic gastropod mollusk in the family Hydrobiidae.

Mercuria is a genus of small brackish water snails or freshwater snails with a gill and an operculum, aquatic gastropod mollusks in the family Hydrobiidae.

Mercuria similis is a species of small freshwater snail with an operculum, an aquatic gastropod mollusk in the family Hydrobiidae.

Mexithauma quadripaludium is a species of freshwater snail, an aquatic gastropod mollusk in the family Hydrobiidae.

Navalis is a genus of minute freshwater snails with an operculum, aquatic gastropod molluscs or micromolluscs in the Hydrobiidae family.

The New Zealand mud snail is a species of very small freshwater snail with a gill and an operculum. This aquatic gastropod mollusk is in the family Tateidae.

Ohridohauffenia is a genus of very small freshwater snails with an operculum, aquatic gastropod mollusks in the family Hydrobiidae, the river snails.
Peringia is a genus of very small snails with gills and an operculum, gastropod mollusks in the family Hydrobiidae.
Peringia ulvae, common name the Laver spire shell or mudsnail, is a European species of very small aquatic snail with gills and an operculum, a gastropod mollusk in the family Hydrobiidae.

Pseudamnicola is a genus of small brackish water snails with an operculum, aquatic gastropod mollusks in the family Hydrobiidae.

Pyrgophorus is a genus of very small freshwater snails with a gill and an operculum, aquatic gastropod molluscs in the family Hydrobiidae.

Pyrgophorus coronatus is a species of very small aquatic snail, an operculate gastropod mollusk or micromollusk in the family Hydrobiidae.

Pyrgophorus spinosus, common name the spiny crownsnail, is a species of very small freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Hydrobiidae.

Pyrgula is a genus of freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Hydrobiidae.

Pyrgula annulata is a species of freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Hydrobiidae.

Pyrgulopsis is a genus of freshwater snails with a gill and an operculum, aquatic gastropod mollusks in the family Hydrobiidae.

Nymphophilus minckleyi is a species of very small freshwater snail, an aquatic gastropod mollusk in the family Hydrobiidae.

Rifia is a species of very small freshwater snail with an operculum, an aquatic operculate gastropod mollusks in the family Hydrobiidae.

Sadleriana is a genus of small freshwater snails, aquatic gastropod mollusks in the family Hydrobiidae.
Sadleriana fluminensis is a land snail from the family Hydrobiidae.

Tanousia is an extinct genus of freshwater snails with gills and an operculum, a gastropod mollusk in the family Lithoglyphidae.
