The former Norwegian Catholic diocese of Hamar existed from 1152 to 1542, when the Protestant Reformation turned it into a bishopric of the Lutheran state church.

It also included some parts of Telemark (the modern municipalities of Hjartdal, Notodden, Seljord, Tinn and Vinje).

He began to build the now ruined cathedral of Christ Church, which was completed about the time of Bishop Paul (1232–1252).

Bishop Thorfinn (1278–1282) was exiled and died at Ter Doest Cistercian Abbey in Lissewege, Flanders.

The last Catholic bishop, Mogens Lauritssøn (1513–1537), was taken prisoner in his castle at Hamar by Truid Ulfstand, a Danish noble, and sent to Antvorskov in Denmark, where he was held until his death in 1542.