Xylophanes cthulhu

Xylophanes cthulhu is a moth of the family Sphingidae. It is known from lowland rainforest in Guatemala and Costa Rica.

The wingspan is 76–82 mm. It is similar to ''Xylophanes neoptolemus.

Adults are on wing year-round in Costa Rica.

The larvae feed on Ludwigia species. They have a snake-like appearance.