Clydonautilus is a genus of nautiloids and type for the Clydonautilidae that has been found in the Upper Triassic of Europe, India, and Timor.

Clydonautilus is the most derived of the Clydonautilitidae, evidenced in its suture.

The shell itself is smooth and involute, with only the outer whorl exposed.

The diagnostic suture has a small median saddle in the ventral lobe which in turn has a smaller shallow lobe.

This prehistoric nautiloid-related article is a stub.