The Terrible Dogfish is a dogfish-like sea monster, which appears in Carlo Collodi's 1883 book The Adventures of Pinocchio as the final antagonist. It is described as being larger than a five-story building, a kilometer long and sporting three rows of teeth in a mouth that can easily accommodate a train. So fearsome is its reputation, that in Chapter XXXIV, it is revealed that the Dogfish is nicknamed "The Attila of fish and fishermen".

Sea monsters are beings from folklore believed to dwell in the sea and are often imagined to be of immense size. Marine monsters can take many forms, including sea dragons, sea serpents, or tentacled beasts. They can be slimy and scaly and are often pictured threatening ships or spouting jets of water. The definition of a "monster" is subjective; further, some sea monsters may have been based on scientifically accepted creatures, such as whales and types of giant and colossal squid.