Thirty-five museum specimens collected in 1926 and 1947–48 vouch for the distinctiveness of an undescribed large mammal, a form of lechwe antelope. Their preservation has allowed comparative analyses of morphological characters to reveal this new species, the Upemba lechwe Kobus anselli sp. nov. It is most similar to the black lechwe K. smithemani and quite distinct from all other known taxa, including topotypical red lechwes K. leche. Prevailing threats and conservation concerns underwrite its formal description after neglect by science for decades. This lechwe is restricted to the Upemba wetlands, Kamalondo depression, south-east Congo basin (Katanga Province, Democratic Republic of Congo), and has declined greatly since the 1970s. Commercial poaching through the 1980s reduced c. 20000 individuals to under 1000 estimated today. Recognition of K. anselli as a distinct evolutionary entity was previously ignored, because the entrenched taxonomy assumed it was just another red lechwe. Its speciation seems to be recent, probably Pleistocene. Lechwes evolved in an archipelago of wetlands formed through vicariance of a more extensive drainage system, the Palaeo-Chambeshi, which extended from Katanga and north-east Zambia across the south-central African plateau, into the Kalahari basin. The Palaeo-Chambeshi was a major endoreic tributary of Palaeo-Lake Makgadikgadi. Its fragmentation isolated lechwes in the Kamalondo depression from wetlands in the Upper Zambezi–Okavango, Upper Kafue, and the Chambeshi and Luapula drainages. The belated discovery of K. anselli emphasizes the region's conservation significance. Because of its high species richness and high endemism, Katanga is a biodiversity hotspot within the encompassing Katanga–Chambeshi region, also covering eastern Angola and much of Zambia. A secure future for the critically endangered Upemba lechwe hinges on reducing adverse human impact and maintaining the integrity of its wetland habitat. Support for protected areas is critical. Maintenance of ecological processes, focused on aquatic systems, is especially important to conserve biodiversity. Recognition of the complex evolutionary history of the region (since the Late Neogene) underpins the scientific foundation for all conservation plans and activities. It prescribes why a regional conservation strategy should encompass the landscape mosaic, structured across neighbouring drainage systems (Lufira, Upper Lualaba and Chambeshi–Luapula rivers). A trans-frontier conservation area will consolidate the protected areas and land use systems of the region in an ecological context.