Platysomus (from Greek: πλατύς platys, 'broad' and Greek: σῶμα sôma 'body')[1] is an extinct genus of ray-finned fish that lived in the Carboniferous and Permian periods.

Platysomus was about 18 centimetres (7.1 in) long, and shaped similarly to the discus fish, having the same flattened body and elongated dorsal and anal fins.

Its jaws were placed vertically under the braincase, giving it a wide gape.

Platysomus is thought to have fed on plankton, and lived in both fresh and salt water.

This article about a prehistoric ray-finned fish is a stub.