Bishopric of Ösel–Wiek

The Bishopric of Ösel–Wiek was a Roman Catholic diocese and a semi-independent prince-bishopric — part of Terra Mariana, the medieval Livonian church state — created on 1 October 1228 as a Latin rite diocese by papal legate William of Modena and simultaneously as a state of the Holy Roman Empire, making it a prince-bishopric: one of the small ecclesiastical states shown on the map, covering the island of Ösel (Saaremaa) and the Wiek region of western Estonia. Due to the repeated shift of the seat of the bishops, it was successively known as the bishopric of Leal (Lihula) from 1234, Perona (Vana-Pärnu) from 1251, and Hapsal (Haapsalu) Castle from 1279, before the seat shifted alone to the castle of Arensburg (Kuressaare) on Ösel, the cathedral chapter remaining at Hapsal. Its prince-bishops ruled their island-and-coast lands, coining and warring amid the Order and the Hansa towns, and the bishopric survived the Middle Ages into the Reformation crisis. The principality ceased to exist in 1560 when its last prince-bishop, Johannes V von Münchhausen, sold it to Denmark, which vested executive power in royally appointed governors; King Frederick II of Denmark's brother Magnus of Livonia, Duke of Holstein, obtained it as an appanage and was elected bishop, abolishing the diocese for his Lutheran rule.