Brune's tryonia (also known as Brune's Springsnail and Brune Spring Snail), scientific name Tryonia brunei, is a species of very small freshwater snail that has a gill and an operculum, an aquatic gastropod mollusks in the family Hydrobiidae. This species is endemic to the United States (Texas). It was formerly listed as Threatened in 1993/1994 and Data Deficient since 1996 until it was changed to Critically Endangered and possibly extinct in 2012; this is because it is found only in Phantom Lake, Balmorhea Lake, has range of less than 100 km², and was last observed in 1993. A 1991 report by the United States Fish and Wildlife Service also listed it as Endangered and they also later noted the unknown population. It is found in firm substratum and on mud before modification.