The Kingdom of Italy and the Vatican sign the Lateran Treaty.

The Kingdom of Italy was a unitary state that existed from 17 March 1861, when Victor Emmanuel II of Sardinia was proclaimed King of Italy, until 10 June 1946, when the monarchy was abolished, following civil discontent that led to an institutional referendum on 2 June 1946. This resulted in a modern Italian Republic. The kingdom was established through the unification of several states over a decades-long process, called the Risorgimento. That process was influenced by the Savoy-led Kingdom of Sardinia, which was one of Italy's legal predecessor states.

The Holy See, also called the See of Rome, the Petrine See or the Apostolic See, is the central governing body of the Catholic Church and Vatican City. It encompasses the office of the pope as the bishop of the apostolic episcopal see of Rome, and serves as the spiritual and administrative authority of the worldwide Catholic Church and Vatican City. Under international law, the Holy See holds the status of a sovereign juridical entity.

The Lateran Treaty was one component of the Lateran Pacts of 1929, agreements between Italy under Victor Emmanuel III and Benito Mussolini and the Holy See under Pope Pius XI to settle the long-standing Roman question. The treaty and associated pacts were named after the Lateran Palace, where they were signed on 11 February 1929. The Italian Parliament ratified them on 7 June 1929.

February 11 is the 42nd day of the year in the Gregorian calendar; 323 days remain until the end of the year.