Unio pictorum, the painter's mussel, is a species of medium-sized freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.

It is called the "painter's mussel" because the shell was historically used as a conveniently sized and shaped receptacle for holding artist's paint.

The native distribution of this species is Europe and Siberia (Russia).

[1] Biotope: water bodies and slower streams.

Right and left valve of the same specimen: