Sternoptyx is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. This is the type genus of the Sternoptychidae, as well as the marine hatchetfish subfamily Sternoptychinae. Sternoptyx have silvery, high, and laterally compressed bodies and large, non-telescopic eyes. They are all relatively small, with even the largest species (S. pseudobscura and S. pseudodiaphana) not exceeding 60 millimetres (2.4 in) standard length.