Australosomus (meaning "southern body") is an extinct genus of prehistoric ray-finned fish that lived during the Early Triassic epoch in what is now Greenland, Kenya, Tanzania, Madagascar, South Africa and Canada (British Columbia).
The type species, Australosomus merlei from Madagascar, was first described as Pristisomus merlei by Ferdinand Priem. A new genus, Australosomus, was later erected for this species by Jean Piveteau.
Australosomus is one of many genera to arise after the Permian-Triassic extinction event, only to die out during the Early Triassic, possibly during a subsequent extinction event.
Most species were marine, except for the African species, which were found in freshwater deposits.
The genus name Australosomus ("southern body") is inaccurate, as Australosomus is known as far north as Canada and Greenland, although the first known remains were described from Madagascar.
Australosomus contains the following species:
Indeterminate remains are known from the Sulphur Mountain Formation of British Columbia and Alberta (Canada). The remains of a potentially associated genus are known from the Late Triassic Chinle Formation of Arizona. Potential remains are known from the Permian-Triassic boundary of Kenya.
Australosomus was an elongate fish. The interlocking scales (3 to 4 times long as wide), deeply forked caudal fin all help to distinguish this genus. It achieved standard lengths of about to .