Weilburg is, with just under 13,000 inhabitants, the third biggest town in Limburg-Weilburg district in Hesse, Germany, after Limburg an der Lahn and Bad Camberg.
The community lies in the Lahn valley between the Westerwald and the Taunus just upstream from where the Weil empties into the river Lahn and 80 km southeast of Koblenz. The Old Town, built on and around a rocky hill, is almost encircled by the Lahn.
Weilburg borders in the north on the communities of Merenberg and Löhnberg (both in Limburg-Weilburg), in the east on the town of Braunfels (Lahn-Dill-Kreis), in the south on the communities of Weilmünster and Weinbach as well as on the town of Runkel, and in the west on the community of Beselich (all in Limburg-Weilburg).
Besides the main town, in which just under 40% of the inhabitants live, the outlying centres of Ahausen, Bermbach, Drommershausen, Gaudernbach, Hasselbach, Hirschhausen, Kirschhofen, Kubach, Odersbach and Waldhausen also belong to Weilburg's municipal area.
It is believed that the earliest traces of settlers in the area around Weilburg are attested by finds from La Tène times from the Scheuernberger Kopf (mountain) near Kirschhofen.
Weilburg was first mentioned in 906 in a chronicle by Abbot Regino of Prüm as a fortification under the name of Wilineburch. Six years later King Conrad I, whose father had been buried in the fortification after having fallen in battle while fighting the Babenbergers near Fritzlar in 906, founded a church and an abbey. In 912, the St. Walpurgis-Chorherrenstift (monastery) was founded. The building, which was built on high ground, afforded the monastery control over the Lahn as well as the Hohe Straße ("High Road") running from Frankfurt to Cologne and the Via Publica from Flanders to Bohemia, which ran nearby.
In 918, the Wilineburg (castle) gained special historic importance when King Conrad I, lying on his deathbed, recommended to his brother Eberhard that he deliver the Imperial insignia to his bitterest rival, the Saxon duke Heinrich (Weilburger Testament).