The Rheider Au (Danish: Rejde Å) is a river of Schleswig-Holstein, Germany.
|54°26′48″N 9°19′35″E / 54.4467°N 9.3263°E|
|Progression||Treene→ Eider→ North Sea|
The Rheider Au is a tributary of the Treene near Hollingstedt. Its source is on the Geest near Schleswig. In the Viking Age the route Eider - Treene - Rheider Au - Schlei served as a navigation way and/or transport or trade route between places to the north and the Baltic Sea, as commercial centres functioned (see Dorestad, Haithabu).