Rock holes are not uncommon in South Africa, yet few descriptions exist and no systematic study has been made of these unique geological features. They occur in a variety of shapes and sizes, and can be classified morphologically as near-surface water reservoirs, potholes, rock basins, irregular holes, and fissure holes. These holes have distinctly different attributes and origins. The first two are in most cases due to erosion in fast-flowing rivers, but the origin of the latter three types is unclear. Some are best explained in terms of glacial plucking while others could be due to a combination of evorsion in pre-Kalahari (possibly Carboniferous?) rivers, and subsequent chemical weathering. The origin of the fissure holes remains unexplained.