The Tasmanian giant freshwater crayfish (Astacopsis gouldi), also called Tasmanian giant freshwater lobster, is the largest freshwater crustacean and the largest freshwater crayfish species in the world. The species is only found in the rivers below 400 meters above sea level in northern Tasmania, an island state of Australia. It is listed as an endangered species on the IUCN Red List due to overfishing and habitat degradation, and it has been prohibited to catch the crayfish since 1998.

Tasmanian giant freshwater lobster is very long-lived, surviving for up to 60 years. It has previously been reported to attain weights of up to 6 kilograms and measure over 80 centimeters long; however, in recent years the majority of larger specimens are 2–3 kilograms. When fully mature the species has no natural predators due to its large size, while smaller individuals can be the prey of platypus, river blackish, and rakali.

Formerly, the species was distributed from the Arthur River in the west and eastwards across northern Tasmania, where it was found in all rivers flowing into the Bass Strait, except for those of the Tamar catchment. Despite the two disjunct ranges, populations across these are genetically similar. The species has been introduced into the North Esk (St Patricks River) and the Derwent catchments where populations have become established. Today, the distribution of Tasmanian giant freshwater lobster is fragmented and limited to less disturbed areas. Large declines in numbers or localized extinctions are thought to have occurred in the Welcome, Montagu, Rubicon, Don, Brid, Boobyalla, Pipers, Ringarooma, Duck, Little and Great Forester Rivers, and Claytons Rivulet. Eastern populations are particularly reduced.

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