FREDERICK I. (1369-1428), elector and duke of Saxony, surnamed the Pugnacious, eldest son of Landgraf Frederick the Severe of Thuringia and of Catherine countess of Henneberg, was born at Altenburg, March 29, 1369. On the death of his father in 1381, he and his two brothers succeeded to the inheritance under the guardianship of their mother, but were compelled to grant a portion of it to their father's two brothers. The death of one of their father's brothers in 1407 occasioned a renewal of the inheri-tance dispute with the remaining brother, and an amicable settlement was not arrived at till 1410. Previous to this Frederick had distinguished himself in wars against the Lithuanians, Hungary, and King Wenzel of Germany; and having in 1420 collected an army against the Hussites, he was for a time so uniformly successful, that in 1423 the emperor Sigismund, in recognition of his valuable services, created him elector and duke of Saxony. With these honours, however, Sigismund also laid upon him the whole burden of the Hussite war; and the result was that, by an overwhelming defeat at Aussig in 1426, nearly all the Saxons capable of bearing arms were either killed or placed hors de combat. Frederick did not long survive this disaster, dying at Altenburg, 4th January 1428. The university of Leipsic was founded by Frederick in 1409.

See life by Spalatin in Mencke's Scriptores rerum Germ.; and life 1 by Horn, Leipsic, 1733.