The fascicularis group of macaques comprises four species: Macaca fascicularis, M. mulatta, M. cyclopis, and M. fuscata. The geographic ranges of M. fascicularis and M. mulatta are parapatric or marginally sympatric, with the former species widely distributed in insular and peninsular Southeast Asia and the latter species widely distributed in southern Asia; M. cyclopis is restricted to Taiwan, and M. fuscata is restricted to the Japanese archipelago. The four species in this group are compared with respect to pelage, external measurements and proportions, cranial characters, caudal vertebrae, molecular biology and genetics, natural history, and reproductive anatomy and behavior. In these species, head and body length and skull length generally increase with latitude, and tail length generally decreases with latitude; in shorter-tailed species, the number and length of caudal vertebrae is progressively reduced. Morphology of the glans penis in fascicularis-group species is uniquely derived among macaque species; morphology of the female tract in this group is similar to that in silenus-group species. Based on morphology and fossil history, a hypothesis is proposed concerning the evolution and dispersal of the fascicularis group.