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.

Its color varies between pale brown and grayish with a glassy shine.

Minimum recorded depth is 0 m.[2] Maximum recorded depth is 3.7 m.[2] The minute hydrobia can be found on seaweeds and mud close to the banks of brackish marshes and estuaries.

The minute hydrobia is a secondary host of a parasitic fluke, Homalometron pallidum.

This has a complex life cycle with the adult phase being found in a small fish, the mummichog, Fundulus heteroclitus.