Sigismund (February 14/15, 1368 - December 9, 1437) was Holy Roman Emperor from 1433 to 1437.

(Non-contemporary) portrait by Albrecht Dürer

The third and last German Emperor and fourth Bohemian king of the Luxembourg dynasty, Sigismund, second son of the Emperor Charles IV, was born in Nuremberg.

Through his marriage to Mary, queen (1382-1385 and 1386-1395) of Hungary, Sigismund became the country's king in 1386 despite opposition among the nobility. In 1396 he organised a crusade to repel the Ottoman Turks, who were threatening Hungary from the south, but the Christian forces were routed at the Battle of Nicopolis (now Nikopol, Bulgaria).

In about 1406 he remarried with Barbara Celjska (Barbara of Celje), daughter of Hermann II, Count of Celje (Cilli).

In 1410 he was elected emperor of the Holy Roman Empire, though his title was not universally recognised until a year later. He was margrave of Brandenburg in 1378-1388 and again from 1411 until 1415, when he granted the territory to Frederick I, Margrave of Brandenburg, burgrave of Nuremberg, making the Hohenzollern family one of the most important in Germany.

It was as king of Bohemia from 1419 in succession to his elder half-brother Wenceslaus IV that Sigismund faced the greatest challenge of his reign. Accused of complicity in the burning of the Czech religious reformer Jan Hus by the Catholic Church leadership in Constance (1415), Sigismund was ejected by the Hussite forces on his attempt to take over the country (1420). A bitter conflict (the Hussite Wars) continued for 15 years, extending across Bohemia's borders. Only in 1437, the year of his death, Sigismund was accepted by the major Czech factions.

Sigismund had no children by Mary of Hungary, but he had a single daughter with Barbara Celjska, Elizabeth (1409-1442). Elizabeth married Albert II, Holy Roman Emperor, who was eventually to succeed his father-in-law as King of Hungary and Bohemia, and as German King.

Names in other languages: German: Sigismund, Hungarian: Zsigmond, Czech: Zikmund, Slovak and Croatian: Žigmund, Slovene: Sigismund Luksemburški