Pisidium lilljeborgii is a species of freshwater bivalve from the family Sphaeriidae.
A moderately swollen (tumid), trapezoidal shell. The umbos are just behind the mid point and described as fairly narrow. The surface (periostracum) is slightly glossy and has coarse, irregular concentric striae. The colour is grey to brownish white. Pisidium lilljeborgii has a less equilateral shape than Pisidium hibernicum 3-4.5mm.
