| Named By: | Eberhard Fraas in 1889 |
| Time Period: | Late Triassic |
| Location: | England - Bromsgrove Sandstone Formation (Finstall Member). Germany - Hassberge Formation, Lowenstein Formation, Stuttgart Formation, Trossingen Formation. Greenland (Oersted Dal Member) - Fleming Fjord Formation. Luxembourg. Poland - Drawno Beds Formation. Russia - Bukobay Formation. Thailand - Huai Hin Lat Formation |
| Size: | Skulls up to 70 centimetres long, largest individuals up to 4.3 meters long |
| Diet: | Carnivore/Piscivore |
| Fossil(s): | Many individuals |
| Classification: | | Chordata | Amphibia | Temnospondyli | Mastodonsauridae | |
| Also known as: | | Mastodonsaurus robustus | |
Cyclotosaurus is an extinct genus of temnospondyl within the family Mastodonsauridae. It was of great size for an amphibian, reaching 3-4.3 m (9.8-14.1 ft) in length with an elongated 70 cm (28 in) skull.