Södermanland County (Södermanlands län) is a county or län on the southeast coast of Sweden. It is often shortened and pronounced as Sörmlands län, or simply Sörmland, which is the dominant pronunciation locally. For example, the name of the local County Council is Region Sörmland. It borders the counties of Östergötland, Örebro, Västmanland, Uppsala, Stockholm and to the Baltic sea. It holds the popular camping route called "Sörmlandsleden" which is a system of trails covering a total of approximately 100 mil (1000 km) of walking paths, in Södermanland.
It is an administrative unit, covering most of the province Södermanland. The eastern parts of the Södermanland province, largely corresponding to the Södertörn area, belong to Stockholm County.