Duchy of Nassau

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Duchy of Nassau Herzogtum Nassau (German)
1806–1866
Flag Coat of arms
The Duchy of Nassau and surrounding states The Duchy of Nassau in the German Confederation in 1815
Status	State of the Confederation of the Rhine (1806–1813) State of the German Confederation (1815–1866)
Capital	Weilburg (1806–1816) Wiesbaden (1816–1866)
Common languages	Moselle Franconian
Government	Constitutional monarchy
Duke
• 1806–1816	Frederick Augustus
• 1816–1839	William
• 1839–1866	Adolph
Historical era	Modern era
• Established	30 August 1806
• Annexed by Prussia	23 August 1866
Currency	Kronenthaler
Preceded by Succeeded by Nassau-Weilburg Nassau-Usingen Principality of Orange-Nassau Hesse-Nassau

The Duchy of Nassau (German: Herzogtum 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.^[1][2] 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.

Today, the Grand Duke of Luxembourg still uses "Duke of Nassau" as his secondary title, and "Prince" or "Princess of Nassau" is used as a title by other members of the grand ducal family. Nassau is also part of the name of the Dutch royal family, which styles itself Orange-Nassau.