A new genus and species of xanthid crab, Cranaothus deforgesi, is described from Chesterfield Island. Cranaothus appears to be closely related to Paramedaeus, Metaxanthops, Macromedaeus, Medaeops, Neoxanthops, Glyptoxanthus and Lipaesthesius, but differs in the form and sculptures on the carapace, as well as structures of the sternum, male abdomen and male first pleopod. The larger cheliped of Cranaothus also possesses a specialized basal cutting tooth on its dactylus.