Prionosuchus is a genus of extremely large temnospondyl amphibians from the Middle Permian (270 million years ago) which was found in an area of what is now Brazil.

The fragmentary remains of this animal have been found in the Pedra do Fogo Formation in the Parnaiba Basin of Northeastern Brazil, and it was described by L.I. Price in 1948. Reaching an estimated length of 9 m (30 ft), Prionosuchus is the largest amphibian ever found.

With an elongated and tapered snout, numerous sharp teeth, long body, short legs, and a tail adapted for swimming, its general appearance was very similar to a modern crocodile, particularly to the gharial, and it probably had a similar lifestyle as an ambush aquatic predator feeding on fish and other aquatic animals.