Petalidium kaokoense, here described as a new species, is only known from the Hartmann Mountains and one other location on the inland plateau in the Kaokoveld Centre of Endemism, northwestern Namibia, where it grows on hillsides and mountain slopes. Diagnostic characters for P. kaokoense include the stout trunk on older plants, white bark, peeling on the younger branches in long, narrow strips, stellate trichomes, short inflorescences of racemoid dichasia with acute linear-oblanceolate or linear-lanceolate bracts, flowers with maroon corollas with the two upper lobes connate towards the base and the lower lobe with two yellow spots near the base. A comparison of some of the more prominent morphological features to differentiate between Petalidium kaokoense and its presumed close relative, the morphologically similar P. physaloides, is provided. Based on IUCN Red List categories and criteria, a conservation assessment of Vulnerable (VU D1) is recommended for the new species. Keywords: endemism, flora, Hartmann Mountains, Kaokoveld, taxonomy.