The county of Sayn- Hachenburg was a former imperial immediacy territory of the Holy Roman Empire in the area of the Westerwald in today's state of Rhineland- Palatinate. The county was created in 1636 by inheritance from the county of Sayn.
The Counts of Sayn built in 1200 to protect an ancient trade route which Hachenburg castle in the Westerwald. She soon became the center of administration in the county of Sayn. After the elder branch of the Counts of Sayn was extinguished in 1606, Hachenburg came to the Counts of Sayn -Wittgenstein- Sayn.
After the death of the last count in 1636, the county was divided into Sayn- old churches and Sayn- Hachenburg. The latter came after a long dispute with the Electorate of Cologne in 1649 with the Countess Louise Juliane ( " The Countess of Sayn " ), whose second daughter Ernestine by marriage to the Counts of Manderscheid - Blankenheim and in 1714 to the Viscount of Kirchberg. 1799 was the county to the princes of Nassau- Weilburg. In connection with the formation of the Confederation of the Rhine (1806 ) Sayn- Hachenburg coincided with Sayn- old churches in the newly built Duchy of Nassau.
The county was part of the Lower Rhenish - Westphalian Circle and the counts at the Lower Rhenish -Westphalian Reichsgraf College. The territory had about 1800 around 250 km ² with about 12,000 inhabitants.
The county extended over the core area around Hachenburg, the spell Maxsain, a share in the pastoral and Burbach ( Kondominat ) and to the parishes Birnbach, Flammersfeld, Hamm and Schöneberg. The parishes were mentioned in 1815 ceded to Prussia. The rest of the territory remained until 1866 when the Duchy of Nassau, came in 1866 to Prussia, and in 1946 part of Rhineland- Palatinate.