Hermann II, count of Croatia

Hermann II, Count of Celje, was a Styrian prince and magnate, most notable as the faithful supporter and father-in-law of the Hungarian king and Holy Roman Emperor Sigismund of Luxembourg. Hermann's loyalty to the King ensured him generous grants of land and privileges that led him to become the greatest landowner in Slavonia. He served as governor of Carniola, and twice as ban of the combined provinces of Slavonia, Croatia and Dalmatia, and was recognized by a treaty in 1427 as heir presumptive to the Kingdom of Bosnia. The House of Celje's rise to power culminated in achieving the dignity of Prince of the Holy Roman Empire. At the peak of his power, he controlled two thirds of the land in Carniola, most of Lower Styria, and exercised power over all of medieval Croatia. Hermann was one of the most important representatives of the House of Celje, having brought the dynasty from regional importance to the foreground of Central European politics.

The Kingdom of Croatia, also known with full diplomatic name Kingdom of Croatia and Dalmatia, entered a personal union with the Kingdom of Hungary in 1102, after a period of rule of kings from the Trpimirović and Svetoslavić dynasties and a succession crisis following the death of king Demetrius Zvonimir.