Eriptychius, is a genus of armored, fossil jawless vertebrates, which lived in the Middle Ordovician (about 450 million years ago) in North America. It is represented by two species, Eriptychius americanus and E. orvigi, known by only scales and armor fragments. A single specimen shows a partly articulated snout, whith traces of a calcified endoskeleton. Isolated branchial plates with a notch for the branchial opening suggest that their overall morphology was rather similar to that of the Astraspida. Eriptychius is found in association with the Astraspida.