The Sihl Valley is the Swiss valley through which the Sihl flows.
The Sihl Valley begins in the Alps of the canton of Schwyz. At the Saas Pass, which leads from the upper Sihl Valley to the Klön Valley, there is a Sihlseeli, a small mountain lake through which the Sihl does not flow. With the Sihlsee, a reservoir in the canton of Schwyz, the Sihl is used to generate electricity for the Swiss Federal Railways. Two dams were built when the power plant was built. The Sihl Valley extends to the gates of the city of Zurich. The Sihl Valley is home to the towns of Biberbrugg, Sihlbrugg, Langnau am Albis, Adliswil and the natural Sihlwald forest as well as the Langenberg wildlife park.
In Sihlbrugg Station, the main Zurich-Zug axis, a continuation of the Gotthard Railway, crosses the Sihl Valley. The railway line to Zurich, which belongs to the Sihltal-Zürich-Uetliberg-Bahn (SZU), branches off from there. The Sihltal is also connected by a two-lane main road, which was the main connection axis from Zurich to the south (Zug, Arth-Goldau, Gotthard) until the opening of the motorway through the Knonaueramt. The connection to the communities on the left bank of Lake Zurich and to those beyond the Albis chain is ensured by various bus lines. From Adliswil, the Adliswil–Felsenegg cable car leads to Felsenegg.