During a comprehensive survey and conservation assessment of populations of Lithops gracilidelineata (Aizoaceae), a population at the northern limit of its distribution was identi ed as profoundly morphologically and ecologically distinct. Following a taxonomic revision of the infraspeci c limits of Lithops gracilidelineata, a new subspecies is described from Mopane-Pachypodium shrubland in northwestern Namibia. Lithops gracilidelineata subsp. mopane S.Hatt can be distinguished by its completely smooth leaf surface relief (vs distinctly rugose), that is very pale, whitish-grey, occasionally with a very pale. pinkish-yellowish tint (vs pale pinkish-beige to very pale, greyish beige in subsp. gracilidelineata; or pinkish or reddish-brown, rarely more beige or yellowish in subsp. brandbergensis) and being almost exclusively 1-headed (vs often 2 – 3 headed). It di ers from all other Lithops species by growing in Mopane shrubland of Colophospermum mopane, with interspersed Pachypodium lealii, amongst quartz pebbles and gravel. Descriptions, photographic illustrations and preliminary conservation assessments are provided for all accepted subspecies of Lithops gracilidelineata. An infraspeci c key is also given, completing a revised classi cation of this threatened and horticulturally important succulent species. Keywords. Africa, Brandberg, Central Namib, Namib Desert, succulent.