Stephen Tvrtko I (Serbo-Croatian: Stjepan/Stefan Tvrtko, Стефан/Стјепан Твртко; c. 1338 – 10 March 1391) was the first king of Bosnia. A member of the House of Kotromanić, he succeeded his uncle Stephen II as Ban of Bosnia in 1353. As he was a minor at the time, Tvrtko's father, Vladislav, briefly ruled as regent, followed by Tvrtko's mother, Jelena. Early in his personal rule, Tvrtko quarreled with his country's Roman Catholic clergy, but later enjoyed cordial relations with all the religious communities in his realm. After initial difficulties – the loss of large parts of Bosnia to his overlord, King Louis I of Hungary, and being briefly deposed by his magnates – Tvrtko's power grew considerably. He conquered some remnants of the neighbouring Serbian Empire in 1373, after the death of it