Poloidion is a genus of green algae in the family Neochloridaceae, containing the single species Poloidion didymos.

[1] It is an extremely rare genus,[2] which has only been recorded once on moist soil and rocks in Austria.

[3] Poloidion consists of cells in groups of two, sometimes four or solitary.

The cell wall is noticeably thickened on one side.

Cells are ovoid, ellipsoidal or irregularly spherical.