Ulrich I, Count of Celje

Ulrich I (c. 1331–1368), eldest son of Frederick I of Celje and Diemut of Wallsee, was a condottiere from his teens. He first saw war in 1346 at Louis the Great of Hungary's unsuccessful siege of Zadar, then fought for Emperor Charles IV on his Italian expedition of 1354 and for Louis against Venice at Treviso in 1354–1355.

From 1359 he headed the house with his brother Hermann. In 1362–1363 he fought for the Habsburg duke Rudolf IV in Friuli and Tyrol and received Kamnik, Žalec and Vojnik in pledge; from 1362 he also served as Habsburg governor of Carniola.

His generalship is usually credited with bringing the Counts of Celje into the high nobility of Central Europe, and his son William, by Adelaide of Ortenburg, married Anna, daughter of Casimir III of Poland, tying the house to royalty.