Hermann I, Count of Celje

Hermann I, Count of Celje, was a Styrian nobleman, who was head of the House of Celje between 1359 and 1385. In the first decade, he ruled together with his older brother Ulrich. After Ulrich's death, Hermann took over the custody of his nephew William and ruled as the de facto head of the family. Under his rule, the House of Celje began expanding its influence from its power base in present-day Slovenia and southern Carinthia to Central Europe and the Balkans. By marriage to the Bosnian princess Catherine, whose exact parentage is disputed, Hermann became the brother-in-law either of the Hungarian and Polish king Louis the Great, or of the Bosnian king Tvrtko I. His son Hermann II further expanded the family's wealth and influence. By the time of his death, Hermann I was the largest landowner in the territory of present-day Slovenia, where his possessions significantly outnumbered those of his Habsburg liege lords.