Shared water is a vital resource for many people around the world. In the ESCWA region, major shared rivers include the Nile, Tigris, Euphrates and Jordan. Many less well-known underground water reservoirs are also shared. Opportunities for negotiation and mutually beneficial use of water also exist in riparian countries, many based on principles of international law and resolutions on shared water. This fact sheet opens with an outline of the general principles of international water law and the major international conventions on shared water, before delineating the major transboundary river basins and shared water aquifers in the ESCWA region.