Friedrich Wilhelm III, Duke of Saxe-Altenburg

The death of his older brother Christian (1663) made him the new heir of the Duchy of Saxe-Altenburg. When his father died in 1669, Friedrich Wilhelm III succeeded him; but, because he was only twelve years old, his maternal uncles, Elector Johann Georg II of Saxony and Duke Maurice of Saxe-Zeitz, assumed the guardianship of the new duke and the regency of the duchy.

Only three years later, the young duke died of smallpox shortly after returning from a trip to Dresden. His burial took place three months later, on 17 July 1672 at his father's tomb in the church of Schloss Altenburg. With his death, the branch of Saxe-Altenburg, founded in 1603, became extinct in the direct male line.

Saxe-Altenburg was split between the branches of Saxe-Gotha and Saxe-Weimar; but, on the basis of the will of the Duke Johann Philipp of Saxe-Altenburg (Friedrich Wilhelm III's uncle) the greater part of the duchy was retained by Saxe-Gotha, because they were the descendants of Elisabeth Sophie, the only daughter of Johann Philipp, who declared her the general heiress of the family in case of the extinction of the male line.

• August Beck: Friedrich Wilhelm III. In: Allgemeine Deutsche Biographie (ADB). Band 7, Duncker & Humblot, Leipzig 1877, p. 794.

• Magister Samuel Haberland: Alte Erinnerungen aus Nobitz II. Band in: kg-nobitz.de [retrieved 21 November 2016].