We sequenced mitochondrial COI and COII genes (1,377 base pairs) of 166 woolly monkeys (Lagothrix) to determine the phylogenetic relationships of tschudii in reference to the other taxa within the genus Lagothrix, to provide the first genetic diversity level estimates for tschudii, and to reconstruct the historical demographic evolution of this taxon. The sample set included, for the first time, 10 individuals of the elusive tschudii taxon sensu Groves from southern Peru and northern Bolivia. Our phylogenetic analyses showed that these 10 exemplars formed a statistically significant and differentiated (molecularly and morphologically) monophyletic clade relative to other traditional subspecies of Lagothrix lagothricha. Therefore, tschudii should be recognized as a fifth subspecies: Lagothrix lagothricha tschudii. The temporal divergence of the ancestors of tschudii and L. l. cana was estimated to have occurred around 1.8 million years ago (MYA). Additionally, mitochondrial diversification within tschudii started no later than 0.96 MYA (Bayesian Inference) or 0.88 MYA (Median Joining-Network), respectively. In contrast to the phylogenetic trees, the FSTstatistic and the gene flow estimates showed L. l. lugens to be the least differentiated taxon of L. lagothricha from L. l. tschudii. Based on genetic distances, L. l. tschudii had the smallest average genetic distance from the other subspecies of L. lagothricha.It was also the taxon within L. lagothricha that had the smallest genetic distance from L. flavicauda. It should be related to L. l. tschudii as the first original taxon in L. lagothricha. Furthermore, the Andean mountains were extremely important in the original diversification of the Lagothrix genus and in the original diversification of L. lagothricha. Although L. l. tschudii has the smallest geographical range of all the taxa of L. lagothricha, its genetic diversity is even higher than in other taxa with wider geographical ranges, such as L. l. lagothricha and L. l. cana. L. l. tschudii showed a very slight demographic increase during the Pleistocene with a decrease of females in the last 10,000 Y, similar to that found for L. l. lugens in a previous study.