The common yabby, Cherax destructor, is an Australian freshwater crustacean. It is in the Parastacidae family. It is listed as a vulnerable species of crayfish by the World Conservation Union (IUCN). But wild yabby populations remain strong, and have expanded into new habitats created by reservoirs and farm dams.
Its common name of "yabby" is also applied to many other Australian Cherax species of crustacean. The name is also applied marine ghost shrimp of the infra-order Thalassinidea. Yabbies occasionally reach up to 30 cm (12 in) in length but are more commonly 10–20 cm (4–8 in) long.
Colour is highly variable and depends on water clarity (how clear it is) and habitat. Yabbies can range from black, blue-black or dark brown in clear waters to light brown, green-brown or beige in dark waters. Yabbies specifically bred to be a vibrant blue colour are now popular in the aquarium trade in Australia.