Saxe-Gotha-Altenburg

Duchy of Saxe-Gotha-Altenburg
Herzogtum Sachsen-Gotha-Altenburg
State of the Holy Roman Empire, State of the Confederation of the Rhine, State of the German Confederation
1680–1826
Flag Coat of arms
Territories of Saxe-Gotha-Altenburg within the Ernestine duchies of Thuringia, before 1826
Capital		Gotha
Government		Principality
Historical era		Early modern Europe
•	Union of Saxe-Gotha and Saxe-Altenburg	1672
•	Duchy established	1680
•	Partitioned between Saxe-Coburg-Saalfeld and Saxe-Hildburghausen	1826
Preceded by Succeeded by Saxe-Gotha Saxe-Altenburg Saxe-Coburg and Gotha Saxe-Hildburghausen

Saxe-Gotha-Altenburg (German: Sachsen-Gotha-Altenburg) was a duchy ruled by the Ernestine branch of the House of Wettin in today's Thuringia, Germany. The extinction of the line in 1825 led to a major re-organisation of the Thuringian states.

In 1640 the sons of the late Ernestine duke John II of Saxe-Weimar divided their paternal heritage (Ernestinische Teilung) whereby Duke Ernest the Pious, a younger son, received the newly established Duchy of Saxe-Gotha. In 1636 Ernest had married Elisabeth Sophie, the only child of Duke John Philip of Saxe-Altenburg. Upon her father's death in 1639, the Duchy of Saxe-Altenburg passed to her uncle Duke Frederick William II and her cousin Frederick William III.

The Duchy of Saxe-Gotha-Altenburg was nominally created in 1672, when Duke Frederick William III of Saxe-Altenburg died at the age of 14 and Ernest the Pious, by his marriage with Elisabeth Sophie, inherited the major part of his possessions. It was common for the Ernestine duchies to merge and split; Ernest's combined duchy was divided again after his death in 1675, and the Duchy of Saxe-Gotha-Altenburg proper came into existence in 1680 with the completion of this division and the accession of his eldest son, Frederick to the subdivision centered on the towns of Gotha and Altenburg.