Cochilius is an extinct genus of interatheriid notoungulate that lived between the Late Oligocene and the lower Miocene in what is now Argentina.

The skull and skeleton show features also found in other similar contemporary or slightly later animals, such as Interatherium and Protypotherium.

In the general proportions of the skull Cochilius was similar to Interatherium, but in some features it was closer to Protypotherium, for example, in the large development of the snout and the median position of the orbits.

[1] The genus Cochilius was first described in 1902 by Florentino Ameghino, based on fossil remains found in Lower Miocene soils in Argentina.

[2] Later, George Gaylord Simpson described the species C. fumensis from Cerro del Humo in Chubut Province, Argentina from slightly older deposits dating to the Late Oligocene.