Reingsen is a part of Ergste, a district of Schwerte, Germany. Before 1975, Reingsen belonged to the county Iserlohn (Kreis Iserlohn). In 2012 Reingsen had a population of 110 inhabitants. It lies south of the river Ruhr near Sauerland and is mainly used for agriculture.
In Reingsen there are two streams, the Lollenbach and the Reingser Bach.