Charles IV (Czech: Karel IV., German: Karl IV., Latin: Carolus IV), born Wenceslaus, was a King of Bohemia and the first King of Bohemia to also become Holy Roman Emperor. He was a member of the House of Luxembourg from his father's side and the House of Přemyslid from his mother's side, which he emphasised, because it gave him two saints as direct ancestors.
He was the eldest son and heir of King John of Bohemia, who died at the Battle of Crécy on 26 August 1346. His mother, Elizabeth of Bohemia, was the sister of King Wenceslas III, the last of the male Přemyslid rulers of Bohemia. Charles inherited the County of Luxembourg from his father and was elected king of the Kingdom of Bohemia. On 2 September 1347, Charles was crowned King of Bohemia.
On 11 July 1346, the prince-electors chose him as King of the Romans (rex Romanorum) in opposition to Emperor Louis IV. Charles was crowned on 26 November 1346 in Bonn. After his opponent died, he was re-elected in 1349 and crowned King of the Romans. In 1355, he was crowned King of Italy and Holy Roman Emperor. With his coronation as King of Burgundy in 1365, he became the personal ruler of all the kingdoms of the Holy Roman Empire.
The reign of Charles IV was characterised by a transformation in the nature of the Empire and is remembered as the Golden Age of Bohemia. He promulgated the Golden Bull of 1356 whereby the succession to the imperial title was laid down, which held for the next four centuries.
He also organized the states of the empire into peace-keeping confederations. In these, the Imperial cities figured prominently. The Swabian Landfriede confederation of 1370 was made up almost entirely of Imperial Cities. At the same time, the leagues were organized and led by the crown and its agents. As with the electors, the cities that served in these leagues were given privileges to aid in their efforts to keep the peace.
He assured his dominance over the eastern borders of the Empire through succession treaties with the Habsburgs and the purchase of Brandenburg. He also claimed imperial lordship over the crusader states of Prussia and Livonia.