Lake Sils (German Silsersee, Romansh: Lej da Segl) is a lake in the Upper Engadine valley, Grisons, Switzerland. It takes its name from the village of Sils im Engadin. The lake lies at an altitude of 1,797 metres above sea level, between Maloja Pass and Lake Silvaplana. It is overlooked by several mountains over 3,000 metres, notably Piz Corvatsch, Piz Grevasalvas and Piz da la Margna. The lake's drainage basin culminates at Piz Fora (3,336 m) and comprises the Vadrec da Fedoz glacier.