The Cyclodomorphus branchialis species group is defined on synapomorphies of scalation. Within this complex, five allopatric species, one with three subspecies, are recognised on morphological grounds: C. branchialis (Günther) of the lower west coast and hinterland, C. maximus (Storr) of the Kimberley, C. melanops melanops (Stirling and Zeitz) widespread in spinifex habitats of the arid north-west, and C. m. elongatus (Werner) widespread in spinifex habitats of the arid south and east of the continent, together with two new species, one from the lower west coast and the other from South Australia, and a new subspecies of C. melanops from chenopod habitats along the southern fringe of the Nullarbor Plain. The morphology, distribution, habitat preferences and reproduction of the seven taxa are described. All primary type specimens are illustrated. A key to the species and subspecies in the genus Cyclodomorphus is provided. Cyclodomorphus branchialis, considered on previous taxonomic opinion to be widespread in arid Australia, is restricted to a small area in Western Australia and is considered vulnerable.