1946 Italian institutional referendum
An institutional referendum (Italian: referendum istituzionale, or referendum sulla forma istituzionale dello Stato) was held by universal suffrage in the Kingdom of Italy on 2 June 1946, a key event of contemporary Italian history. Until 1946, Italy was a kingdom ruled by the House of Savoy, reigning since the unification of Italy in 1861 and previously rulers of the Kingdom of Sardinia.
Source: Wikipedia — 1946 Italian institutional referendum (CC BY-SA 4.0)