Prince-Bishopric of Warmia

The Prince-Bishopric of Warmia (Polish: Biskupie Księstwo Warmińskie, German: Fürstbistum Ermland) was a semi independent ecclesiastical state, a Prussian bishopric under the jurisdiction of the Archbishopric of Riga that was a protectorate of the Monastic state of the Teutonic Knights (1243–1466) and a protectorate of Kingdom of Poland, later part of the Polish-Lithuanian Commonwealth after the Peace of Thorn (1466-1772)

Originally founded as the Bishopric of Ermland, it was created by William of Modena in 1243 in the territory of Prussia after its conquest by the Teutonic Knights during the Northern Crusades. The diocesan cathedral chapter constituted in 1260. While in the 1280s the Teutonic Order succeeded to impose the simultaneous membership of all capitular canons in the Order in the other three Prussian bishoprics, Ermland's chapter maintained its independence. So the Ermland's chapter could repel outside influence when electing its bishops. Thus the Golden Bull of Emperor Charles IV names the bishops as prince-bishops, a rank not awarded to the other three Prussian bishops (Culm, Pomesania, and Samland).

By the Second Peace of Thorn (1466) the prince-bishopric - like other western areas of Teutonic Prussia - seceded and formed a part of Royal Prussia, which adopted the King of Poland as sovereign in a personal union. After in 1569 Royal Prussia joint the Polish-Lithuanian Commonwealth Ermland's autonomy gradually faded.

After the First Partition of Poland in 1772, the annexing Kingdom of Prussia secularised the prince-bishopric as a state. Its territory, Warmia (German: Ermeland), was incorporated into the Prussian province of East Prussia. King Frederick II of Prussia confiscated the landed property of the prince-bishopric and assigned it to the Kriegs- und Domänenkammer in Königsberg. In return he made up for the enormous debts of then Prince-Bishop Ignacy Krasicki.

By the Treaty of Warsaw (18 September 1773), King Frederick II guaranteed the free exercise of religion for the Catholics, so the religious body of the Roman Catholic diocese continued to exist, known today as the Roman Catholic Archdiocese of Warmia.