The frilled lizard, also known as the frillneck lizard, frill-necked lizard or frilled dragon, is a species of lizard in the family Agamidae. It is native to northern Australia and southern New Guinea. This species is the only member of the genus Chlamydosaurus. Its common names come from the large frill around its neck, which usually stays folded against the lizard's body. It reaches 90 cm (35 in) from head to tail and can weigh 600 g (1.3 lb). Males are larger and more robust than females. The lizard's body is generally grey, brown, orangish-brown, or black in colour. The frills have red, orange, yellow, or white colours.

Deimatic behaviour or startle display means any pattern of bluffing behaviour in an animal that lacks strong defences, such as suddenly displaying conspicuous eyespots, to scare off or momentarily distract a predator, thus giving the prey animal an opportunity to escape. The term deimatic or dymantic originates from the Greek δειματόω (deimatóo), meaning "to frighten".