Ernest I, called Ernest the Pious (; 25 December 1601 - 26 March 1675), was duke of Saxe-Gotha and Saxe-Altenburg, later united as Saxe-Gotha-Altenburg. He was a surviving son of Johann II, Duke of Saxe-Weimar and Dorothea Maria of Anhalt. He is remembered for rebuilding and reforming his lands after the