Königssondergau

Königssondergau (German for "King's Special District") was a Frankish "gau" (district) which existed in the area around Wiesbaden, Germany, from Frankish times until the end of the 12th century.

It extended from Walluf in the west to Kriftel in the east, from the Rhine-Main confluence in the south to the Taunus in the north. It was regarded as "private property" of the Frankish kings. In the Carolingian age a court of law located at Mechtildshausen became an imperial court where death sentences were pronounced and carried out on behalf of the Emperor.

Just before his death, the last count of the Königssondergau, Udalrich of Ebbensten (d. 1123) gave over Eppstein Castle and the eastern part of the gau as a fiefdom to the Archbishopric of Mainz who, in turn enfoeffed the territory to the Lords of Eppstein in between 1180 and 1190. Also in the late 12th century, the western parts of the gau including Wiesbaden were enfoeffed to the Duchy of Nassau.