Lake Zug (German: Zugersee) is a lake in Central Switzerland, situated between Lake Lucerne and Lake Zurich . It stretches for 14 km (8.7 mi) between Arth and the Cham-Zug bay. The Lorze as the main feeder river empties its waters into the lake at its northern extremity, but 1 km (0.6 mi) further west issues from the lake to pursue its course towards the Reuss. Due to this poor feeding, Environmental protection is very important as the lake would suffer long term damage if polluted as the second of the rivers, Rigiaa, feeds only a marginal amount into the lake at its southern end. Already a great part of the fauna in the deep parts of the lake has been lost.

The lake is mostly within the borders of the Canton of Zug , with about 10 square kilometres (3.9 sq mi) at its southern end in the canton Schwyz , while the Canton of Lucerne claims about 2 km2 (0.77 sq mi) to the north of Immensee.