The Karongi (Kibuye) sheet of the Geological Map of Rwanda at 1:100,000 scale covers the northwestern quarter of the square degree S 3/29. The topographic back ground of the map was produced from a 10m resolution Digital Terrain Model (DTM) acquired by Rwanda in 2010, supplemented by public GIS datasets accessible via the internet from the R w anda National R esources Authority (RNRA), the Regional Centre for Mapping of Resources for Development (RCMRD) and the World Bank (WB). The geological limits were digitized by the Royal Museum for Central Africa (RMCA) at a scale of 1:50,000 from the 1991 Kibuye (Karongi) geological map (Kibuye, S 3/29 NW , 1/100.000) that was produced at the time essentially from field observations supplemented with air photo interpretations. This geological dataset was updated with support from the Belgian technical cooperation Agency (Enabel), in the scope of RMCA s contribution to the Sustainable Development of Mining in Rwanda project (a DfID UK funded programme). The update is based on data and insights on the geological history of Rwanda and surrounding regions that became available since the publication of the 1991 map. Three new fieldtransects that yielded nearly 500 observation points and 16,000 field observation points extracted from the archives of the RMCA delivered the direct field information needed. Interpretations of the airborne geophysical data (magnetism and radiometry) flown in the 1980-ies, but published only in the early 1990-ies, were used to identify respectively granitic intrusive bodies present in the study area and deep-seated structural magnetic anomalies under southwestern Rwanda. All these datasets w ere then combined with a geomorphological interpretation of the DTM to produce a new geological dataset for the area.