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 standard length.
- Sternoptyx diaphana <small>Hermann, 1781</small> (Diaphanous hatchetfish)
- Sternoptyx obscura <small>Garman, 1899</small>
- Sternoptyx pseudobscura <small>R. C. Baird, 1971</small> (Highlight hatchetfish)
- Sternoptyx pseudodiaphana <small>Borodulina, 1977</small> (False oblique hatchetfish)
Fossils of this genus show that they have existed at least since the Early Oligocene, about 30 million years ago.