River width is a fundamental parameter of river hydrodynamic simulations, but no global‐scale river width database based on observed water bodies has yet been developed. Here we present a new algorithm that automatically calculates river width from satellite‐based water masks and flow direction maps. The Global Width Database for Large Rivers (GWD‐LR) is developed by applying the algorithm to the SRTM Water Body Database and the HydroSHEDS flow direction map. Both bank‐to‐bank river width and effective river width excluding islands are calculated for river channels between 60S and 60N. The effective river width of GWD‐LR is compared with existing river width databases for the Congo and Mississippi Rivers. The effective river width of the GWD‐LR is slightly narrower compared to the existing databases, but the relative difference is within ±20% for most river channels. As the river width of the GWD‐LR is calculated along the river channels of the HydroSHEDS flow direction map, it is relatively straightforward to apply the GWD‐LR to global and continental‐scale river modeling.

The African continent hosts some of the largest freshwater systems worldwide, characterized by a large distribution and variability of surface waters that