The Ems (; ) is a river in northwestern Germany. It runs through the states of North Rhine-Westphalia and Lower Saxony, and discharges into the Dollart Bay which is part of the Wadden Sea. Its total length is . The state border between the Lower Saxon area of East Friesland (Germany) and the province of Groningen (Netherlands), whose exact course is the subject of a border dispute between Germany and the Netherlands, runs through the Ems estuary.