He is not to be confused with his cousin Landgrave Frederick IV of Thuringia, the son of Landgrave Balthasar. He was the eldest son of Frederick III, Landgrave of Thuringia, and Catherine of Henneberg. After the death of his uncle William I, Margrave of Meissen in 1407, he governed the Margraviate of Meissen together with his brother William II as well as with his cousin Frederick IV (son of Balthasar), until their possessions were divided in 1410 and 1415.
In the German town war of 1388 he assisted Frederick V of Hohenzollern, burgrave of Nuremberg, and in 1391 did the same for the Teutonic Order against Wladislaus II of Poland. In the prosecution of this enterprise Frederick spent large sums of money, for which he received various places in Bohemia and elsewhere in pledge from Sigismund, who further rewarded him on 6 January 1423 with the vacant electoral Duchy of Saxony-Wittenberg. And Fredericks formal investiture followed at Ofen on the 1 August 1425.
Thus ascended Frederick IV, who called himself Frederick I now, to the duke and elector.
Frederick died in 1428 at Altenburg. He was buried as the first Wettin in the princely chapel in Meissen Cathedral.
Catherine, died young;
Frederick II, Elector of Saxony (1412–1464);
Sigismund, Bishop of Würzburg, (3 March 1416 – 24 December 1471);
Anna, (5 June 1420 – 17 September 1462), married to Louis I, Landgrave of Hesse;
Catherine, (1421 – 23 August 1476, Berlin), married to Frederick II, Elector of Brandenburg;
Henry, (21 May 1422 – 22 July 1435);
William III, Duke of Luxemburg (1425–1482), Landgrave of Thuringia;
married firstly, in 1446, Archduchess Anne of Austria (1432–1462)
married secondly, in 1463, Catherine of Brandenstein († 1492).
