The Barbary macaque, Macaca sylvanus (Linnaeus, 1758), is systematically reviewed, based on a study of 103 specimens and survey of relevant literature. This review includes analyses of external characters, cranial characters, DNA variation, and karyology. Information also is presented concerning natural history, reproduction, fossils, and taxonomic history. Current knowledge of geographic variation in M. sylvanus is insufficient to warrant recognition of subspecies. Although M. sylvanus is now restricted to northwestern Africa, fossil evidence suggests that this species is a relict of the ancestral macaque stock that originated in Africa ca. 7-6 million years ago (Ma) and dispersed to Eurasia ca. 6–5 Ma. Macaques formerly were widely distributed in Europe, but became extinct there ca. 0.100–0.020 Ma; macaques have survived in Asia and are now represented there by ca. 20 species. An annotated gazetteer lists 166 localities where M. sylvanus has been collected, observed, or reported.