A new species of Hylomyscus, H. heinrichorum, is described from mountains in western Angola. Based on morphological traits and cranial morphometry, the new species is assigned to the H. anselli species group and is hypothesized to be most closely related to H. anselli Bishop proper, a species named from Zambia. Members of both the H. anselli and H. denniae species groups occupy the Afromontane Biotic Zone, found in various mountain systems to the south and east of the Congo Basin. Evidence is reviewed that supports the independent radiation of these two species groups within montane forest from different Guineo-Congolian ancestral stocks.