Trosaån
The Trosaån in Trosa
The Trosaån in Vagnhärad
The Trosaån in winter
Template: Infobox River / Obsolete
Trosaån is a 12 km long river, which rises in the south-eastern Södermanland Sillen at the lake. It flows through the town and finally empties into Vagnhärad Trosa in the Baltic Sea.
1997 slipped in a landslide several houses in the town Vagnhärad in the Trosaån.