50°47′02″N 7°40′34″E / 50.784025°N 7.676218°E
Opperzau is a community of the German municipality Windeck, in the Rhein-Sieg district, in the south-eastern part of North Rhine-Westphalia. The southern part of Opperzau is named Oppertsau, which belongs to the municipality Fürthen and belongs to Rhineland-Palatinate. It is located at the middle course of the river Sieg.