Freshwater Ecoregions of the World, (FEOW) provides a new global biogeographic regionalization of the Earth’s freshwater biodiversity. Covering virtually all freshwater habitats on Earth, this first-ever ecoregion map, together with associated species data, is a useful tool for underpinning global and regional conservation planning efforts, particularly to identify outstanding and imperiled freshwater systems; for serving as a logical framework for large-scale conservation strategies; and for providing a global-scale knowledge base for increasing freshwater biogeographic literacy.