| Named By: | Henri Marie Ducrotay de Blainville in Blainville in 1818 |
| Time Period: | Late Permian |
| Location: | England - Raisby Formation, and Germany - Kupferschiefer Formation |
| Size: | About 30 centimetres long |
| Diet: | Carnivore |
| Fossil(s): | Many individuals |
| Classification: | | Chordata | Osteichthyes | Actinopterygii | Palaeonisciformes | |
| Also known as: | | Palaeoniscus | |
Palaeoniscum is an extinct genus of ray-finned fish from the Permian period of Europe and North America.
Palaeoniscum had a torpedo-shaped body 30 centimetres (12 in) in length, with a deeply forked caudal fin and tall dorsal fin, indicating that it was a fast swimmer. It was probably an active predator, feeding on other fresh water fish. Its sharp teeth could be replaced when lost, a trait also seen in modern day sharks. Like other early ray-finned fish, Palaeoniscum had air sacs connected to the mouth which served as a primitive swim bladder.