The Duchy of Siewierz was a Silesian duchy with its capital in Siewierz. The area was part of the original Duchy of Silesia established after the death of Duke Bolesław III Wrymouth in 1138 during the times of the fragmentation of Poland. Since 1443, after its acquisition by Archbishop Zbigniew Cardinal Oleśnicki for 6,000 silver groats, it was, alongside the Duchy of Nysa, the only ecclesiastical duchy in the region (ruled by a bishop of the Catholic Church). On many levels this tiny principality was almost a 'country within a country': it had its own laws, treasury and army.