The Duchy of Saxe-Weimar-Eisenach (Herzogtum von Sachsen-Weimar-Eisenach) was created in 1809 by the merger of the Duchies of Saxe-Weimar and Saxe-Eisenach , which had been in personal union since 1741, when the Saxe-Eisenach line had died out. It became a Grand Duchy in 1815. In 1877, it officially changed its name to the Grand Duchy of Saxony (Großherzogtum von Sachsen), but this name was rarely used. The Grand Duchy came to an end in 1918 with the other German monarchies, and the state was merged into the new state of Thuringia two years later.

Saxe-Weimar-Eisenach had an area of 3,617 km² and a population of 388,000 (1905). Its capital was Weimar.

Dukes of Saxe-Weimar-Eisenach, 1809-1815

• Carl August (Duke of Saxe-Weimar and Eisenach from 1758) 1809-1815

Grand Dukes of Saxe-Weimar-Eisenach, 1815-1918

• Carl August 1815-1828
• Carl Friedrich 1828-1853
• Carl Alexander 1853-1901
• Wilhelm Ernst 1901-1918

Heads of the House of Saxe-Weimar-Eisenach, 1918-present

• Grand Duke Wilhelm Ernst 1918-1923
• Hereditary Grand Duke Carl August 1923-1988
• Prince Michael 1988-