The intraspecific phylogeography of Grant's gazelles Nanger granti was assessed with mitochondrial DNA control region sequences. Samples of 177 individuals from 17 Kenyan and Tanzanian populations were analysed. Three highly divergent, reciprocally monophyletic lineages were found, with among group net nucleotide distances of 8–12%. The three lineages—notata, granti and petersii—grouped populations according to their geographic origin, encompassing populations in the north, southwest, and east, respectively. The mtDNA lineages reflected distinct evolutionary trajectories, and the data are discussed in reference to the four currently recognised subspecies. We suggest Grant's gazelles be raised to the superspecies Nanger (granti) comprising three taxonomic units corresponding to the three mtDNA lineages. There was no evidence of gene flow between the notata and granti lineages, despite their geographic proximity, suggesting reproductive isolation. These constitute evolutionary significant units within the adaptive evolutionary framework. Due to its restricted geographic distribution and genetic and morphological distinctiveness, we suggest the petersii lineage be raised to the species Nanger (granti) petersii within the Grant's gazelles superspecies.