| Named By: | Morris & Roberts in 1862 |
| Time Period: | Early Carboniferous-Late Carboniferous |
| Location: | British Isles |
| Size: | Up to 45 centimetres long |
| Diet: | Carnivore |
| Fossil(s): | Several specimens |
| Classification: | | Chordata | Chondrichthyes | Holocephali | Chimaeriformes | Deltoptychiidae | |
Deltoptychius is an extinct species of cartaliginous fish related to the modern chimaeras. It lived in the Carboniferous period of present-day Europe.
Although it emerged over 300 million years ago, Deltoptychius was similar in appearance to modern-day chimaeras, possessing a long, whip-like tail and large, wing-like pectoral fins that it probably used to glide through the water. Deltoptychius`s large eyes allowed it to hunt in deep waters, crushing shellfish between solid tooth plates in its mouth.