Chironex fleckeri, commonly known as the Australian box jelly and nicknamed the sea wasp, is a species of extremely venomous box jellyfish found in coastal waters from northern Australia and Papua New Guinea to Indonesia, East Timor, Cambodia, Malaysia, Singapore, the Philippines and Vietnam. It has been described as "the most lethal jellyfish in the world", with at least 64 known deaths in Australia from 1884 to 2021.