琉森湖（英：Lake Lucerne,德：Vierwaldstättersee（四森林州湖））位于瑞士中部，处于四森林州之间。四森林州包括琉森州（Luzern）、乌里州（Uri）、施维茨州（Schwyz）及以前的翁特瓦尔登州（Unterwalden，即现在的上瓦尔登半州（Obwalden）及下瓦尔登半州（Nidwalden））。

湖泊面积大约115.2km²，是瑞士境内第五大湖泊。琉森湖夹在阿尔卑斯山的群峰之间，因此形状显得十分不规则。首先罗伊斯河（Reuss）在乌里州的Flüelen自南向北流入琉森湖，在乌里州境内的部份称为Urnersee。然后湖水于施维茨州与Muota河汇流，湖形自此转为东西向。然后加入自下瓦尔登半州流入的Engelberger Aa河，转向北方，湖面突然收窄，进入琉森州后变阔成为十字形。十字形湖面的西南翼由上瓦尔登半州的Sarner Aa河流入，东北翼突入施维茨州，湖水进入西北翼于琉森市流出罗伊斯河。

Lake Lucerne (German:Vierwaldstättersee, lit. "Four Forested Settlements Lake", French:lac des Quatre-Cantons, Italian:lago dei Quattro Cantoni) is a lake in central Switzerland and the fourth largest in the country.

The lake has a complicated shape, with several sharp bends and four arms. It starts in the south-north bound Reuss Valley between steep cliffs above the Urnersee from Flüelen towards Brunnen to the north before it makes a sharp bend to the west where it continues into the Gersauer Becken. Here is also the deepest point of the lake with 214 m (702 ft). Even more west of it is the Bouchser Bucht, but the lake sharply turns north again through the narrow opening between the Unter Nas (lower nose) of the Bürgenstock to the west and the Ober Nas (upper nose) of the Rigi to the east to reach the Vitznauer Bucht. In front of Vitznau below the Rigi the lake turns sharply west again to reach the center of a four-arm cross, called the Chrütztrichter (cross funnel). Here converge the Vitznau Bay with the Küssnachtersee from the north, the Luzernersee from the west, and the Horwer Bucht and the Stanser Trichter to the south, which is to be found right below the northeast side of the Pilatus and the west side of the Bürgenstock. At the very narrow pass between the east dropper of the Pilatus (called Lopper) and Stansstad the lake reaches its southwestern arm at Alpnachstad on the steep southern foothills of the Pilatus, the Alpnachersee. The lake drains its water in Lucerne from the literally correctly translated western arm Lake of Lucerne into the Reuss.