Crayfish, also known as crawfish, crawdads, freshwater lobsters, mountain lobsters, mudbugs or yabbies, are freshwater crustaceans resembling small lobsters, to which they are related; taxonomically, they are members of the superfamilies Astacoidea and Parastacoidea.

They breathe through feather-like gills.

Some species are found in brooks and streams where there is running fresh water, while others thrive in swamps, ditches, and rice paddies.