Wahnbach

{{Short description|River in Germany}}

{{Expand German|topic=geo|date=October 2011|Wahnbach}}

{{Infobox river

| name = Wahnbach

| image =

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| mouth_location = Sieg

| mouth_coordinates = {{coord|50.7939|N|7.2717|E|source:wikidata-and-enwiki-cat-tree_region:DE|display=it}}

| progression = {{RSieg}}

| subdivision_type1 = Country

| subdivision_name1 = Germany

| subdivision_type2 = State

| subdivision_name2 = North Rhine-Westphalia

| length = {{convert|29.4|km|abbr=on}} {{GeoQuelle|DE-NW|GSK3C}}

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Wahnbach is a river of North Rhine-Westphalia, Germany. It flows into the Sieg near Hennef.