Frederick I, Count of Celje

Frederick I (c. 1300–1359), born lord of Žovnek in the Savinja Valley, founded the house that would dominate Slovenian and Croatian history in the early fifteenth century. In 1322 the Counts of Heunburg died out in the male line, and he inherited their castles in Carinthia, Carniola and Styria, among them Celje.

His cousin Ulrich V of Pfannberg and Countess Elizabeth contested the inheritance, but with his brother-in-law Ulrich of Walsee's help he held nearly all of it by 1333. Loyal to the Habsburgs like his father, he served as their captain of Carniola and the Windic March, smoothed their takeover of 1335 and fought Charles of Luxembourg's forces in Carinthia.

In April 1341 Emperor Louis IV made him first Count of Celje. By Diemut of Wallsee he left sons Ulrich and Hermann.