Erebia cassioides, the common brassy ringlet, is a member of the subfamily Satyrinae of family Nymphalidae.

Subspecies include:[1] On the basis of studies of enzymatic electrophoresis and of mitochondrial DNA the subspecies Erebia cassioides arvernensis should be considered a distinct species named Erebia dromus (Fabricius, 1793),[4] which is distributed in the western Pyrenees, in the western Alps and in Apennines.

[5][6] This European endemic species is present in Spain (Cantabrian mountains, Pyrenees), France (Pyrenees, Massif Central and the western and eastern Alps), Italy, Switzerland, Romania (Carpathians), Bulgaria (Rila and Pirin Mountains.

[10] These small butterflies have a brown forewings with a metallic-greenish shine, the so-called "brassy ringlet".

The underside of the forewings is orange with a brownish border and two small ocelli at the apex, while the hindwings are shiny silvery gray and ocher.