Ernst I, Duke of Saxe-Altenburg (German: Ernst I. Friedrich Paul Georg Nikolaus von Sachsen-Altenburg) (16 September 1826 inHildburghausen – 7 February 1908 inAltenburg), was a duke ofSaxe-Altenburg. He was the first son ofGeorg, Duke of Saxe-Altenburg andMarie Luise of Mecklenburg-Schwerin. In 1853, he succeeded his father as Duke ofSaxe-Altenburg. He was of a retiring disposition and he took little active part in running the country. After a reign that lasted 55 years, he died without a living direct male heir; because of this, he was succeeded by his nephew,Ernst.
^abStaatshandbücher für das Herzogtum Sachsen-Altenburg (1902), "Genealogie des Herzoglichen Hauses Sachsen-Altenburg"pp. 1-2
^Staatshandbuch für das Großherzogtum Sachsen / Sachsen-Weimar-Eisenach (1851), "Großherzogliche Hausorden" p.8Archived 2020-07-06 at theWayback Machine