Bienertia is a very interesting genus with its unique C4 photosynthesis in a single cell. Recent investigations on the taxonomy of the genus using a multidisciplinary approach revealed the existence a third species of this genus from the margin of Dasht-e Kavir (desert plain) in central Iran, thus adding a fourth terrestrial C4 plant lacking Kranz anatomy. The flattened leaves, the semi-inferior ovary resulting from adnation of the perianth with the ovary, in addition to cotyledon morphology and hypocotyl length, provide evidence for the existence of a new species. The new species is here described as Bienertia kavirense Akhani spec. nov., after its locality at the margin of the Kavir. The gametic chromosome complement of the new species is n = 9. The carbon isotope values (δ13C) showed a C4 photosynthesis which is remarkably less negative than in the two other species of Bienertia. Detailed information on the morphology, leaf anatomy, and ecology of the new species is provided, and the new association “Bienertio kavirense–Cornulacetum aucheri” is described as a unique plant community occurring at the margin of the Dasht-e Kavir. Only a few species, such as Salsola annua (Bunge) Akhani comb. nov., associate with B. kavirense.