The Derwent flounder, Taratretis derwentensis, is a flatfish of the family Pleuronectidae. It is a demersal fish that lives on sand and mud bottoms in shallow coastal waters, at depths of between 3 and 50 metres (9.8 and 164.0 ft). Its native habitat is the south-western Pacific, particularly the south-east coast of Australia, from New South Wales to South Australia and Tasmania. It grows to at least 9 centimetres (3.5 in) in length, and can reach up to 12 centimetres (4.7 in).