Ernst I, Duke of Saxe-Altenburg (German: Ernst I. Friedrich Paul Georg Nikolaus von Sachsen-Altenburg) (16 September 1826 in Hildburghausen – 7 February 1908 in Altenburg), was a duke of Saxe-Altenburg. He was the first son of Georg, Duke of Saxe-Altenburg and Marie Luise of Mecklenburg-Schwerin. In 1853 he succeeded his father as Duke of Saxe-Altenburg. He was of a retiring disposition and he took little active part in running the country. After a reign that lasted fifty five years, he died without a living direct male heir; because of this, he was succeeded by his nephew, Ernst.

Marriage

He was married in Dessau on 28 April 1853 to Agnes of Anhalt-Dessau (1824–1897). Agnes was a sister of Friedrich I, Duke of Anhalt. They had two children:

Honours and decorations

• Ernestine duchies: • * Joint Grand Master of the Saxe-Ernestine House Order, 3 August 1853 • * Service Award Cross (25 years) • Saxe-Weimar-Eisenach: Grand Cross of the White Falcon, 24 February 1849 • undefined: Knight of the Rue Crown, 1848 • Ascanian duchies: Grand Cross of Albert the Bear, 3 January 1852; with Swords, 1872 • Baden: • * Knight of the House Order of Fidelity, 1881 • * Knight of the Order of Berthold the First, 1881 • undefined: Knight of St. Hubert, 1853 • Brunswick: Grand Cross of Henry the Lion, with Swords, 1876 • undefined: • * Knight of St. George, 1855 • * Grand Cross of the Royal Guelphic Order • * Grand Cross of the Order of Ernst August • Schaumburg-Lippe: • * Cross of Honour of the House Order of Lippe, 1st Class with Crown • * Military Merit Medal • Mecklenburg: • * Grand Cross of the Wendish Crown, with Collar • * Military Merit Cross, 2nd Class (Schwerin) • Nassau Ducal Family: Knight of the Gold Lion of Nassau • Oldenburg: Grand Cross of the Order of Duke Peter Friedrich Ludwig, with Golden Crown and Collar, 9 February 1852 • Kingdom of Prussia: • * Knight of the Black Eagle, with Collar • * Knight of the Red Eagle, 1st Class • * Grand Commander of the Royal House Order of Hohenzollern • * Knight of Honour of the Johanniter Order • * Iron Cross, 2nd Class • Württemberg: Grand Cross of the Württemberg Crown, 1868

Ancestry