Lake Brienz is a lake just north of the Alps, in the Canton of Berne in Switzerland. It has a length of about , a width of and a maximum depth of . Its area is , and the surface is above the sea-level. It is fed by the upper reaches of the Aar river at its eastern end and by the Lütschine river, flowing from the valleys of Grindelwald and Lauterbrunnen, at its south-western corner. It flows out into a further stretch of the Aar river at its western end. The culminating point of the lake's drainage basin is the Finsteraarhorn at 4,274 metres above sea level.