The narrow, northwestern branch of Obersee is also called Überlinger See (English: Lake Überlingen).

The distinctive, northwestern arm and 21 square kilometres (8.1 sq mi)-large Lake Überlingen (Standard German of Germany: Überlinger See), named after Überlingen, is part of the Upper Lake Constance, as well as the Bay of Bregenz, and the Constance Hopper.

The countries that border the lake are Switzerland, with its cantons of Thurgau and St. Gallen, Austria, with its federal state of Vorarlberg, and Germany, with its federal states of Baden-Württemberg and Bavaria.

The exact location of the border between the riparian states within the south-eastern part of Obersee have never been jointly agreed upon (see Lake Constance); only the smaller northwestern water of Lake Überlingen is completely within German territory.

In the Middle Ages the dominant term was Lacus Bodamicus, or in German Bodensee.