During its history, the status of the region of Croatia has changed several times. Conquered by the Roman Empire in the first century AD, the region then underwent a period of migration before the duchy of Croatia was established in 818. The first king of Croatia, Tomislav, was recognised as such in 925. The kingdom survived until it was brought into a personal union with Hungary in 1102. This continued until the sixteenth century when Croatia faced Ottoman invasions, and was divided into territories, some under Habsburg and some under Ottoman control. Territorial disputes continued until the Croatian-Hungarian settlement of 1868 when Croatia and Slavonia were united, with the kingdom of Dalmatia remaining under Austrian control. From 1918-1941 the kingdom of Serbs, Croats, and Slovenes was established and survived until its occupation by Germany and Italy during World War Two, upon which a puppet state was created. After World War Two a Socialist Federal Republic of Yugoslavia was created, of which Croatia was part, and monarchy was abolished.
The changing kingdoms of Croatia saw many queen consorts, and the occasional queen regnant, during its history. You can find out more about one of them, Helen of Zadar, below!
Johnson, Lonnie. Central Europe. Enemies, Neighbors, Friends. Third Edition. Oxford: Oxford University Press, 2010
Nagy, Balázs, and Marcell Sebők, eds. The Man of Many Devices, Who Wandered Full Many Ways: Festschrift in Honor of János M. Bak. Budapest: CEU Press, 1999.
Tanner, Marcus. Croatia. A History from the Middle Ages to the Present Day. London: Yale University Press, 2019.