Open AccessReasons for adopting the name Acacia karroo Hayne are considered and the nomenclature and synonymy are dealt with. A broad description of the species is provided. The relationship of A. karroo to the closely related A. seyal Del., A. hockii De Wilid. and the glandular podded Acacia species is mentioned. Acacia karroo Hayne, which is the most widespread Acacia in southern Africa, is an extremely variable species which occupies a diverse range of habitats. The range of variation within A. karroo, and in particular in Natal, is considered. At least six entities are recognizable within A. karroo in Natal. The nature and range of variation within these entities is considered. No infraspecific categories are recognized within A. karroo.