EISENACH, a principality of Germany, forming part of the possessions of the grand duke of Saxe-Weimar-Eisenach. It consists of one principal and several detached portions, the former being bounded on the N. by Prussian Saxony, E. by Saxe-Gotha and Saxe-Meiningen, S. by Bavaria, and W. by Hesse-Cassel. This principality was formerly an independent possession; but on the death of the last duke in 1741, it fell by succession to the dukes of Saxe-Weimar, of whose dominions it now forms a circle. It has an area of 466 square miles, and in 1853 had 82,321 inhabitants. The general character of the soil is mountainous, and the grain produced is not equal to the wants of the inhabitants.