Kronberg im Taunus is a town in the Hochtaunuskreis district, Hesse, Germany and part of the Frankfurt Rhein-Main urban area. Before 1866, it was in the Duchy of Nassau; in that year the whole Duchy was absorbed into Prussia. Kronberg lies at the foot of the Taunus, flanked in the north and southwest by forests. A mineral water spring also rises in the town.

The Duchy of Nassau was an independent state between 1806 and 1866, located in what is now the German states of Rhineland-Palatinate and Hesse. It was a member of the Confederation of the Rhine and later of the German Confederation. Its ruling dynasty, now extinct, was the House of Nassau. The duchy was named for its historical core city, Nassau, although Wiesbaden rather than Nassau was its capital. In 1865, the Duchy of Nassau had 465,636 inhabitants. After being occupied and annexed into the Kingdom of Prussia in 1866 following the Austro-Prussian War, it was incorporated into the Province of Hesse-Nassau. The area today is a geographical and historical region, Nassau, and Nassau is also the name of the Nassau Nature Park within the borders of the former duchy.