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. This version of the FEOW, modified by The Nature Conservancy, includes additional tabular data describing Major Habitat Types (MHTs, similar to terrestrial biomes). These MHTs were developed by TNC and WWF, Inc., but have not undergone rigorous review and are as of yet unpublished. All ecoregions are nested within the eleven MHTs' boundaries.