Claudiosaurus is an extinct genus of diapsid reptile from the Permian period of Madagascar.
Claudiosaurus was one of the first members of the Neodiapsida, a group of reptiles containing most diapsids except the primitive Araeoscelidia. It had a relatively long body and neck, reaching on overall length of about 60 centimetres (2.0 ft). It is presumed to have been partially oceanic, living its life in a way similar to the modern Marine Iguana. The main reason for this theory is that the skeleton included substantial amounts cartilage, rather than bone, indicating it had trouble supporting its weight on land. In particular, the sternum was poorly developed, which would have made walking difficult out of water. Instead, it probably swam by undulating its body and tail, and holding its legs close to the body to increase streamlining.