Saxe-Eisenach () was the name of three different Ernestine duchies that existed at different times in Thuringia. The chief town and capital of all three duchies was Eisenach.

History
The first Duchy of Saxe-Eisenach was created in 1596 for Johann Ernst, younger son of Johann Frederick II of Saxe-Coburg-Eisenach.

In 1633, the Wettin line died out, and Johann Ernst inherited it, but he died heirless in 1638, and the territories of Saxe-Gotha and Saxe-Eisenach were split between Saxe-Weimar and Saxe-Altenburg.

In 1640 Saxe-Eisenach was again separated off from Saxe-Weimar for Albert, son of John II of Saxe-Weimar, but after just four years he too died without an heir, and Saxe-Eisenach was then divided between Saxe-Gotha and Saxe-Weimar, ruled by his brothers Ernst and Wilhelm.

In 1662 Wilhelm, Duke of Saxe-Weimar died, leaving four children: Johann Ernst, Adolf Wilhelm, Johann Georg and Bernhard. Adolf Wilhelm, got Eisenach, but he had to share this with his younger brother Johann Georg. Johann Georg eventually took an allowance from the duchy instead of taking part in the government, and moved to live in the small town of Marksuhl. Adolf William’s first four sons died soon after birth. In 1668 he died, just before of the birth of his fifth child, Wilhelm August, who became the new Duke of Saxe-Eisenach from his birth, with Johann Georg as regent. A sickly boy, he died in 1671 at only two years old, and Johann Georg I became the duke of Saxe-Eisenach.

Saxe-Eisenach changed again in 1672. Frederick William III of Saxe-Altenburg died and his lands were split. The line of Johann Georg I ruled Saxe-Eisenach for 69 years, until Duke Wilhelm Heinrich died heirless in 1741. Ernst August I of Saxe-Weimar, Wilhelm's second cousin, inherited Saxe-Eisenach; he and his successors ruled Saxe-Weimar and Saxe-Eisenach in a personal union until 1809, when the duchies were formally merged into the Duchy of Saxe-Weimar-Eisenach.

Dukes of Saxe-Eisenach

First creation 
Created in 1572 as Saxe-Coburg-Eisenach
1596 divided into Saxe-Coburg and Saxe-Eisenach
 Johann Casimir (1572 – 1633, ruled Saxe-Coburg)
 Johann Ernst (1572 – 1638, retained Saxe-Eisenach)
Divided between Saxe-Altenburg and Saxe-Weimar

Second creation 
 Albrecht (1640 – 44)
Divided between Saxe-Gotha and Saxe-Weimar

Third creation 
 Adolf Wilhelm (1662 – 68)
 Wilhelm August (1668 – 71)
 Johann Georg I (1671 – 86)
 Johann Georg II (1686 – 98)
 Johann Wilhelm (1698 – 1729)
 Wilhelm Heinrich (1729 – 41)
Line extinct

Personal union with Saxe-Weimar 
 Ernst August I (1741-1748)
 Ernst August II (1748-1758)
 Karl August (1758-1809)
Merged with Saxe Weimar into Saxe-Weimar-Eisenach

Related pages
 Ernestine duchies

Other websites
 German genealogies

1596 establishments
1590s establishments in Europe
16th-century establishments in Germany
1638 disestablishments
1640 establishments
1640s establishments in Europe
17th-century establishments in Germany
1644 disestablishments
1640s disestablishments in Europe
1662 establishments
1660s establishments in Europe
1809 disestablishments
1800s disestablishments in Germany
House of Wettin
States of the Confederation of the Rhine
States of the Holy Roman Empire