Marstonia ozarkensis, common name the Ozark pyrg, is a species of very small or minute freshwater snails with an operculum, aquatic gastropod molluscs in the family Hydrobiidae.

This species was endemic to Missouri and Arkansas[2] in the United States and was presumed extinct by the U.S.

Fish and Wildlife Service as of December 2018.

[3] This species was named after the Ozarks, a highland region of the United States.

This Hydrobiidae-related article is a stub.