The Namaqua rock mouse, Aethomys namaquensis (A. Smith, 1834), is a widely distributed species in southern Africa. Analysis of geographic variation among samples of A. namaquensis from southern Africa across a more comprehensive geographical coverage than has hitherto been considered for the species suggests the recognition of four subspecies: A. n. namaquensis (A. Smith, 1834); A. n. lehocla A. Smith, 1836; A. n. alborarius Peters, 1852; and A. n. monticularis Jameson, 1909, which differ both in cranial size and shape. The geographical limits of the proposed subspecies broadly coincide with major phytogeographical zones of southern Africa. This infraspecific taxonomic treatment of southern African A. namaquensis reduces the number of previously recognized subspecies or referred taxa from 16 to four. While the subspecies designations in this study are probably valid in terms of their constitution, their boundaries, however, require further refinement involving other systematic techniques, such as DNA analysis. Keywords: Namaqua rock mouse, infraspecific variation, morphometrics, cranial morphology, southern Africa.