see text Sphaerius is a genus of beetles in the family Sphaeriusidae, comprising 18 species.

They are typically found along the edges of streams and rivers, where they feed on algae; they occur on all continents except Antarctica.

The overall form of the beetle is convex, glossy, dark brown or black with some markings possible.

The beetles occur in a variety of damp environments, including mud, under stones, among plant roots and leaf litter, and in mosses in bogs.

The name was inappropriately replaced with "Microsporidae" (by changing the genus name to Microsporus), but this act has been superseded by a return to the use of Sphaerius and a reformation of the family name as Sphaeriusidae.