Thuwathu is the Rainbow Serpent of the Lardil people of Mornington Island in the Gulf of Carpentaria, and the central creator figure of their cosmology. In the best-known narrative, recorded by the Lardil artist Goobalathaldin (Dick Roughsey) and documented ethnographically by David McKnight, the serpent refused shelter to his sister, the shore-bird Bulthuku, and her infant during cold rain; in revenge she burned his shelter, and the burning serpent rolled and writhed across the country, gouging the swamps, creeks and rivers and leaving parts of his body as sacred story places. Thuwathu is counted among the principal ancestral beings who, with Marnbil and his companions, established the form of the Lardil land and the moral order that governs the people.