The Sihl is a river in Switzerland. It rises at Drusberg in the Canton of Schwyz. It passes through the Sihlsee near Einsiedeln, and then enters the Canton of Zurich, flowing through the Sihl valley (Sihltal) at the foot of the Albis, passing the Sihlwald, the largest remaining deciduous forest of the Swiss plateau, near Langnau am Albis.