Rengsdorf is a municipality in the district of Neuwied, in Rhineland-Palatinate, Germany. It is situated in the Westerwald, approx. 10 km north of Neuwied.

Rengsdorf is the seat of the Verbandsgemeinde ("collective municipality") Rengsdorf-Waldbreitbach.

Today Rengsdorf is a regional well known Heilklimatischer Kurort [de] ("air spa") with popular forest walks. The Rheinsteig, a 320 km (200 mi) hiking trail, also passes by the village.

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  Town hall and seat of the Verbandsgemeinde
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  The Bismarcksäule [de] in Rengsdorf, a Bismarck tower, inaugurated in 1903
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  Park of the Obere Mühle in 2014
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  The wooden shelter Nonnenley on the Ley of the same name
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  The brook Laubach between Ehlscheid and Rengsdorf

Lohmann & Rauscher, a developer, producer, and seller of medical devices and hygiene products has one of its headquarters in Rengsdorf (the other one in Vienna, Austria). The headquarter of Berge & Meer [de], a travel operator, is located in Rengsdorf as well as the one of Winkler und Dünnebier Süßwarenmaschinen [de], a confectionery machinery manufacturer. Since 1997, Winkler und Dünnebier Süßwarenmaschinen GmbH belongs to the Maschinenbau Runkel GmbH, a mechanical engineering company that is also seated in Rengsdorf. Other companies with their seat in Rengsdorf are meta Trennwandanlagen GmbH & Co. KG, a manufacturer for cubicle systems, personal and storage lockers and changing rooms and the monte mare Betriebs GmbH, a bath operator.

• Fritz Henkel (1848–1930), founder of the Henkel Group
• Norbert van Heyst (b. 1944), senior commander in the German Army and commander of the ISAF