April 13: edit
- 1055 - Victor II is consecrated pope.
- 1204 - The Fourth Crusade sacks Constantinople.
- 1250 - The Seventh Crusade is defeated in Egypt, Louis IX of France is captured.
- 1256 - The Grand Union of the Augustinian order when Pope Alexander IV issues a papal bull Licet ecclesiae catholicae.
- 1598 - Henry IV of France issues the Edict of Nantes, allowing freedom of religion to the Huguenots.
- 1742 - George Frideric Handel's oratorio Messiah makes its world-premiere in Dublin, Ireland.
- 1829 - The British Parliament grants freedom of religion to Roman Catholics.