The Blue Yabby (Cherax destructor), also known as the common yabby, cyan yabby, or simply yabby, is an Australian freshwater crustacean in the Parastacidae family. It is listed as a vulnerable species of crayfish by the International Union for Conservation of Nature (IUCN), though 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 infraorder Thalassinidea).
Yabbies occasionally reach up to 30 cm (12 in) in length, but are more commonly 10–20 cm (4–8 in) long.
Color 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 color are now popular in the aquarium trade in Australia.