The spiny trapdoor spiders (Idiopidae) of the Cataxia bolganupensis-group from south-Western Australia are revised, and six species are recognized: C. barrettae sp. nov., C. bolganupensis (Main, 1985), C. colesi sp. nov., C. melindae sp. nov., C. sandsorum sp. nov. and C. stirlingi (Main, 1985). All species exhibit extreme short-range endemism, with allopatric sky-island distributions in mesic montane habitats of the Stirling Range, Porongurup Range and Mount Manypeaks. A molecular phylogenetic analysis of mitochondrial cytochrome c oxidase subunit I (CO1) and cytochrome b (CYB) sequences complements the morphological taxonomy, along with a key to species and detailed information on their distributions and habitat preferences. All six species are assessed as 'endangered' using IUCN criteria, with the major threatening processes being the spread of the plant pathogenic fungus Phytophthora (causing dieback), climate change and inappropriate fire regimes.