The Principality of Erfurt (Fürstentum Erfurt) existed from 1806 to 1814 and included Erfurt and the surrounding land, including the Grafschaft Blankenhain. It was subordinate directly to the Emperor of the French.
The Principality of Erfurt became subordinate to Napoleon I as imperial state domain (domaine réservé à l'empereur), along with the Grafschaft Blankenhain, after the defeat of Prussia in the Battle of Jena and Auerstedt, while the surrounding Thuringian states joined the Confederation of the Rhine.