Bishopric of Ösel–Wiek
The Bishopric of Ösel–Wiek (Estonian: Saare-Lääne piiskopkond; German: Bistum Ösel–Wiek; Low German: Bisdom Ösel–Wiek; contemporary Latin: Ecclesia Osiliensis) was a Roman Catholic diocese and a semi-independent prince-bishopric — part of Terra Mariana (Old Livonia) in the Holy Roman Empire. The bishopric covered what are now Saare, Hiiu, Lääne counties and the western part of Pärnu county of Estonia.