Debeerius is a genus of chondrichthyan from the Mississippian age Bear Gulch Limestone of Montana, United States.

One species, D. ellefseni, is known, which is preserved in very fine detail.

Melanin preserved in fossils of D. ellefseni indicates it possessed dark stripes down the length of its body.

The jaw suspension of Debeerius was autodiastylic (two jointed).

This article about a prehistoric cartilaginous fish is a stub.