The Duchy of Saxe-Weimar-Eisenach (German: Herzogtum Sachsen-Weimar-Eisenach) was created in 1809 when the Ernestine duchies of Saxe-Weimar and Saxe-Eisenach were formally joined into one state. The two duchies had shared the same ruler since 1741, which is when the Saxe-Eisenach line had died out. It became a Grand Duchy in 1815.