Kochelsee or Lake Kochel is located 70 kilometres south of Munich on the edge of the Bavarian Alps. The western third of the lake lies within the borders of the town of Schlehdorf, while the rest belongs to Kochel am See. The southern edge of the lake lies up against the mountains and the northern shore is bordered by bog lands. The history of the settlement of Kochel begins with Birg bei Altjoch, a rock extrusion on the shore of the lake. The name Kochel is derived from the Latin cocula meaning head or cone.
The Loisach flows into the lake at Schlehdorf and flows out at Kochel am See. A similar amount of water flows into the lake from the Isar through the Lake Walchen Power Plant.