AbstractThe Congo Basin is of global significance for biodiversity and the water and carbon cycles. However, its freshwater availability and distribution remain relatively unknown. Using satellite data, here we show that currently the Congo Basin’s Total Drainable Water Storage lies within a range of 476 km³to 502 km³, unevenly distributed throughout the region, with 63% being stored in the southernmost sub-basins, Kasaï (220–228 km³) and Lualaba (109–169 km³), while the northern sub-basins contribute only 173 ± 8 km³. We further estimate the hydraulic time constant for draining its entire water storage to be 4.3 ± 0.1 months, but, regionally, permanent wetlands and large lakes act as resistors resulting in greater time constants of up to 105 ± 3 months. Our estimate provides a robust basis to address the challenges of water demand for 120 million inhabitants, a population expected to double in a few decades.