We describe a new genus and species of troglomorphic scorpion from Ledge Cave, Barrow Island, off the north-western coast of Western Australia. This troglobite scorpion was initially difficult to place within the superfamily Scorpionoidea Latreille on account of its unusual morphology. Based on cladistic analysis, we demonstrate that this scorpion is phylogenetically most closely related to the endemic Australian genus Urodacus Peters (Urodacidae Pocock). The new taxon, named Aops oncodactylus, gen. et sp. nov., is the first troglobitic urodacid and the first troglobitic scorpion recorded from continental Australia. In light of this discovery, we re-assess the known diversity of troglobitic scorpions and the troglomorphic adaptations (troglomorphies) of cavernicolous scorpions. A distinction is recognised between the exclusive occurrence in cavernicolous habitats and the presence of troglomorphies, which are exhibited by some endogean (humicolous) scorpions. The definition of troglobitic scorpions is limited to species that are both restricted to cavernicolous habitats and exhibit pronounced troglomorphies. Only 20 scorpion species meet both criteria and are considered unequivocally troglobitic according to this definition.