Spiny lobsters, also known as langustas, langouste, or rock lobsters, are a family (Palinuridae) of about 60 species of achelate crustaceans, in the Decapoda Reptantia. Spiny lobsters are also, especially in Australia, New Zealand, Ireland, South Africa, and the Bahamas, called crayfish, sea crayfish, or crawfish, terms which elsewhere are reserved for freshwater crayfish.

The Achelata is an infra-order of the decapod crustaceans, holding the spiny lobsters, slipper lobsters and their fossil relatives.