The Pseudonautilidae is a family of Jurassic and Lower Cretaceous cephalopods belonging to the same major group as modern Nautilus, the Nautilaceae, but forming a different branch from the Nautilidae. They were contemporary with ammonites (order Ammonitida) which comprise an entirely different set of shelled cephalopod stocks.

The Pseudonautilidae is a family of Jurassic and Lower Cretaceous cephalopods belonging to the same major group as modern Nautilus, the Nautilaceae, but forming a different branch from the Nautilidae. They were contemporary with ammonites (order Ammonitida) which comprise an entirely different set of shelled cephalopod stocks.