The common yabby, Cherax destructor, is an Australian freshwater crustacean in the Parastacidae family. It is listed as a vulnerable species of crayfish by the World Conservation Union (IUCN), though the validity of this listing is questionable; 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 (as well as to 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 and habitat; yabbies can range from black, blue-black or dark brown in clear waters to light brown, green-brown or beige in turbid waters. Yabbies specifically bred to be a vibrant blue colour are now popular in the aquarium trade in Australia.