Forsån (Swedish: "Rapids' Stream") is a stream in southern Stockholm, Sweden. It is also known as Stortorpsån and Forsen. Leaving lake Magelungen calmly by a small sandy beach, Forsån's upper reach passes through a furrow blown in the 1860s to lower the level of the lake resulting in the present wide torrents passing through the bedrock. In contrast, the last 500 metres of the course are characterized by flat shores and stagnant, overgrown waters. The stream has a vigorous population of signal crayfish and is the only winter habitat in Stockholm for white-throated dipper.