Rohnstadt is a village (Ortsteil) of the municipality of Weilmünster in the district of Limburg-Weilburg in central Hesse.

Rohnstadt is located in the eastern Hintertaunus, about three kilometers southwest of the Weilmünster core, embedded in a high hollow between the Hofwald, Hühnerküppel, Riesenkopf and Steinchen elevations in the Taunus Nature Park.

Celtic fortifications (ring walls) on the Riesenkopf, the Riesenburg, and on the Hühnerkuppel indicate an older settlement in this area.

A prehistoric long-distance route, the so-called Hessenstrasse (also called Hünerstrasse), which connected the Rhineland with northern Hesse, used to take its course here.

In the course of the territorial reform in Hesse, on 31 December 1970 the former market town of Weilmünster in the Oberlahn district merged voluntarily with the previously independent municipalities of Aulenhausen, Dietenhausen, Ernsthausen, Laimbach, Langenbach, Laubuseschbach, Lützendorf, Möttau, Rohnstadt and Wolfenhausen to form the new enlarged municipality of Weilmünster.

Today, Rohnstadt, like many places in the neighborhood, has developed into a commuter village in the Frankfurt Rhine-Main metropolitan area.

Until 1970, the Rohnstadt municipal administration (town hall) was housed on the upper floor.