- May 4 Bourbon reign restored in France
- May 4 King Ferdinand VII of Spain signs the Decree of the 4th of May, returning Spain to absolutism
- May 5 British attack Fort Ontario, Oswego, New York
- May 17 Denmark cedes Norway to Sweden (National Day)
- May 17 Norwegian constitution passed by constitutent assembly at Eidsvoll
- May 17 Occupation of Monaco changes from French to Austrian
May 30 Napoleonic Wars: War of the Sixth Coalition - the Treaty of Paris (1814) is signed returning French borders to their 1792 extent.