Frederick I, the Belligerent or the Warlike (German: Friedrich der Streitbare; 11 April 1370 – 4 January 1428), a member of the House of Wettin, ruled as Margrave of Meissen from 1407 and Elector of Saxony (as Frederick I) from 1423 until his death.
The danger to Germany from the Hussites induced Frederick to ally himself with Emperor Sigismund; and he took a leading part in the war against them, during the earlier years of which he met with considerable success. For his victory at the Battle of Brüx in 1421, Frederick was granted the ranks of Duke and Elector. 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 as duke and elector. Thus spurred to renewed efforts against the Hussites, the elector was endeavouring to rouse the German princes to aid him in prosecuting this war when the Saxon army was almost annihilated at Aussig on the 16 August 1426.
After the death of his brother William, Frederick became the ruler over the entire possession of the House of Wettin except Thuringia.
Frederick died in 1428 at Altenburg. He was buried as the first Wettin in the centre of what is now known as the Princes Chapel in Meissen Cathedral. The cathedral is now accessible to the public for a small fee and the tomb is readily seen.