Ägerisee, Glacial lake in Zug, Switzerland

Ägerisee is a 7.2 km² glacial lake in the canton of Zug, lying at 724 m above sea level in the Schwyz Alps. Its main inflow is the Hüribach and its outflow the Lorze; the shores belong to Oberägeri and Unterägeri. The western bank carries no road, only a hiking trail, so timber felled there is floated across the water on trucks.

The lake witnessed the Battle of Morgarten in 1315, a turning point in Swiss history when local confederates defeated a major regional power. This pivotal moment shaped the region's future and remains central to how locals understand their past.

The lake is still used for timber floating, a practice now found nowhere else in Switzerland: wood felled on the roadless western shore is floated across to the other side for onward transport by lorry. Since 1890 passenger boats have run on the lake, continued since 2002 by Ägerisee Schifffahrt AG with two motor vessels.

The shoreline is accessible from several points, with public beaches and swimming areas open during warmer months. Parking is available near the main villages, and walking paths run along much of the lake's perimeter.

The lake's ice is not always open for use: in late January 2006, after more than two months of low temperatures and a 12 cm thick layer of good ice, areas were released for use for the first time since 1981, at the boat harbour in Oberägeri and at the two boat stations in Unterägeri.