Bithynia leachii is species of small freshwater snail with an operculum, an aquatic prosobranch gastropod mollusk in the family Bithyniidae.
The width of the shell is 3–7 mm. The height of the shell is 4–8 mm. The colour is brown or grey. There are 4 to 4.5 very convex whorls forming a short cone with a very deep suture in comparison to Bithynia tentaculata. The spire is shorter and less sharp than in Bithynia tentaculata. The aperture and operculum upside are smoothly rounded. The aperture is without a sharp point on the upper corner.
It is a Palearctic species found in North Africa and Europe to East Siberia.
This species requires clean, calcium-rich water, which is slow-running and thickly weeded.
