The Wiesbaden Region (German: Regierungsbezirk Wiesbaden) was one of three administrative regions (along with Darmstadt Region and Kassel Region) from which the state of Hesse was formed in 1945.
Following the Prussian annexations after the Austro-Prussian War of 1866, the administrative region of Wiesbaden was founded on February 22, 1867, comprising the formerly independent Duchy of Nassau, the Landgraviate of Hesse-Homburg and the formerly Free City of Frankfurt, previously states of the German Confederation. The Wiesbaden Region was one of the two political subdivisions (along with Kassel Region) within the province of Hesse-Nassau (the Prussian province formed in 1868 including, besides the Wiesbaden Region, further the former Electorate of Hesse, previously another member of the German Confederation).
In 1945 the northwestern part of region was dissected, when the Wiesbaden Region was divided between the American and the French zone of occupation in Germany. The bulk of region with the city of Wiesbaden continued to exist as a region within the new state of Hesse. The dissected northwest formed a new region, the Montabaur Region within Rhineland-Palatinate.
In 1968, the region was dissolved, and its territory was merged in the Darmstadt Region.
Unlike other Prussian regions the Wiesbaden Region was not only an administrative entity of the Prussian government, but its pertaining counties formed a body, the Bezirksverband Nassau or Wiesbaden (about: regional association), with its own representative assembly (Nassauischer Kommunallandtag Wiesbaden, i.e. Nassau Communal Diet, existed between 1866 and 1933) and premises provided and tasks fulfilled for the entirety of the counties within the region. These tasks comprised among others schools, traffic installations, sanitary premises, hospitals, cultural institutions, jails etc. The same was the case in the Kassel Region with an own assembly (Kurhessischer Kommunallanddtag Kassel).