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.