Lake Constance (German: Bodensee, pronounced [ˈboːdn̩ˌzeː] (listen)) refers to three bodies of water on the Rhine at the northern foot of the Alps: Upper Lake Constance (Obersee), Lower Lake Constance (Untersee), and a connecting stretch of the Rhine, called the Lake Rhine (Seerhein). These waterbodies lie within the Lake Constance Basin (Bodenseebecken) in the Alpine Foreland through which the Rhine flows.The lake is situated where Germany, Switzerland, and Austria meet. Its shorelines lie in the German states of Baden-Württemberg and Bavaria, the Swiss cantons of St. Gallen, Thurgau, and Schaffhausen, and the Austrian state of Vorarlberg. The actual location of the border is disputed.
The Alpine Rhine forms in its original course the Austro-Swiss border and flows into the lake from the south. The High Rhine flows westbound out of the lake and forms (with the exception of the Canton of Schaffhausen) the German-Swiss border as far as to the city of Basel.The most populous towns on the Upper Lake are Constance (German: Konstanz), Friedrichshafen, Bregenz, Lindau (Bodensee), Überlingen and Kreuzlingen. The largest town on the Lower Lake is Radolfzell am Bodensee. The largest islands are Reichenau in the Lower Lake, and Lindau and Mainau in the Upper Lake.
While in English and the Romance languages, the lake is named after the city of Constance, the German name derives from the village of Bodman (municipality of Bodman-Ludwigshafen), in the northwesternmost corner of the lake.