Lateran Treaty in the context of "Christianity in Vatican City"

Vatican City, officially the Vatican City State (Italian: Stato della Città del Vaticano; Latin: Status Civitatis Vaticanae), often shortened as the Vatican, is a landlocked sovereign city-state. Ruled by the pope, it is an enclave within Rome and serves as the administrative centre of the Catholic Church. Vatican City is governed by the See of Rome, commonly known as the Holy See, itself a sovereign entity under international law, which maintains its temporal power, governance, diplomacy, and spiritual independence. Vatican is also used as a metonym for the Holy See, which is the central governing body of the Catholic Church and Vatican City, comprising the pope and the Roman Curia. The independent state of Vatican City came into existence in 1929 via the Lateran Treaty between the Holy See and the Kingdom of Italy, which spoke of it as a new creation, not as a vestige of the much larger Papal States (756–1870), which had previously encompassed much of Central Italy.

With an area of 48.99 hectares (121 acres) and a population of about 882 in 2024, it is the smallest sovereign state in the world both by area and by population. It is among the least populated capitals in the world. As governed by the Holy See, Vatican City State is an ecclesiastical or sacerdotal-monarchical state ruled by the pope, who is the bishop of Rome and head of the Catholic Church; the highest state functionaries are all Catholic clergy of various origins. The Holy See dates to early Christianity and is the principal episcopal see of the Catholic Church, which in 2018 had about 1.329 billion baptized Catholics in the world, in the Latin Church and 23 Eastern Catholic Churches. After the Avignon Papacy (1309–1377) the popes have mainly resided at the Apostolic Palace within what is now Vatican City, although at times residing instead in the Quirinal Palace in Rome or elsewhere.

The pope is the bishop of Rome and the head of the worldwide Catholic Church. He is also known as the supreme pontiff, Roman pontiff, or sovereign pontiff. From the 8th century until 1870, the pope was the sovereign or head of state of the Papal States, and since 1929 of the much smaller Vatican City State. From a Catholic viewpoint, the primacy of the bishop of Rome is largely derived from his role as the apostolic successor to Saint Peter, to whom primacy was conferred by Jesus, who gave Peter the Keys of Heaven and the powers of "binding and loosing", naming him as the "rock" upon which the Church would be built. The current pope is Leo XIV, who was elected on 8 May 2025 on the second day of the 2025 papal conclave.

While his office is called the papacy, the jurisdiction of the episcopal see is called the Holy See. The word see comes from the Latin for 'seat' or 'chair' (sede, referring in particular to the one on which the newly elected pope sits during the enthronement ceremony). The Holy See is a sovereign entity under international law; it is headquartered in the distinctively independent Vatican City, a city-state which forms a geographical enclave within the conurbation of Rome. It was established by the Lateran Treaty in 1929 between Fascist Italy and the Holy See to ensure its political and spiritual independence. The Holy See is recognized by its adherence at various levels to international organizations and by means of its diplomatic relations and political accords with many independent states.

The Holy See exercised temporal power, as distinguished from its spiritual and pastoral activity, while the pope ruled the Papal States in central Italy. The Papal States ceased to exist following the capture of Rome in 1870 by the Royal Italian Army, after which its remaining territories were annexed to the Kingdom of Italy. The Lateran Treaty of 1929 later established the Vatican City, a small city-state where the Holy See currently exercises temporal powers.

The Archbasilica of Saint John Lateran (officially the Major Papal, Patriarchal and Roman Archbasilica, Metropolitan and Primatial Cathedral of the Most Holy Savior and Saints John the Baptist and the Evangelist in Lateran, Mother and Head of All Churches in Rome and in the World), commonly known as the Lateran Basilica or Saint John Lateran, is the Catholic cathedral of the Diocese of Rome in the city of Rome, Italy. It serves as the seat of the bishop of Rome and head of the worldwide Catholic Church, the pope. The only "archbasilica" in the world, it lies outside of Vatican City proper, which is located approximately four kilometres (2+1⁄2 miles) northwest. Nevertheless, as properties of the Holy See, the archbasilica and its adjoining edifices enjoy an extraterritorial status from Italy, pursuant to the terms of the Lateran Treaty of 1929. Dedicated to Christ the Saviour, in honor of John the Baptist and John the Evangelist, the place name – Laterano (Lateran) – comes from an ancient Roman family (gens), whose palace (domus) grounds occupied the site. The adjacent Lateran Palace was the primary residence of the pope until the Middle Ages.

The church is the oldest of the four major papal basilicas, and it is one of the Seven Pilgrim Churches of Rome. Founded in 324, it is the oldest public church in the city of Rome, and the oldest basilica in the Western world. It houses the cathedra of the Roman bishop, and it has the title of ecumenical mother church of the Catholic faithful. The building deteriorated during the Middle Ages and was badly damaged by two fires in the 14th century. It was rebuilt in the late 16th century during the reign of Pope Sixtus V. The new structure's interior was renovated in the late 17th century, and its façade was completed in 1735 under Pope Clement XII.

Benito Amilcare Andrea Mussolini (29 July 1883 – 28 April 1945) was an Italian politician and journalist who was the dictator of Italy during the Fascist era from the March on Rome in 1922 until his overthrow in 1943. He founded the National Fascist Party (PNF) and served as Prime Minister of Italy from 1922, later adopting the title Duce ("leader") of Italian fascism. Mussolini first organized the Italian Fasces of Combat in 1919, which evolved into the PNF that established a totalitarian regime. As the founder of fascism, Mussolini was a key inspiration and contributor to the rise of similar movements across Europe during the interwar period.

Mussolini was originally a socialist politician and journalist at the Avanti! newspaper. In 1912, he became a member of the National Directorate of the Italian Socialist Party (PSI), but was expelled for advocating military intervention in World War I. In 1914, Mussolini founded a newspaper, Il Popolo d'Italia, and served in the Royal Italian Army until he was wounded and discharged in 1917. He eventually denounced the PSI, his views pivoting to focus on Italian nationalism, and founded the fascist movement which opposed egalitarianism and class conflict, instead advocating "revolutionary nationalism" transcending class lines. In October 1922, following the March on Rome, he was appointed prime minister by King Victor Emmanuel III. After removing opposition through his secret police and outlawing labour strikes, Mussolini and his followers consolidated power through laws that transformed the nation into a one-party dictatorship. Within five years, he established dictatorial authority by legal and illegal means and aspired to create a totalitarian state. In 1929, he signed the Lateran Treaty to establish Vatican City.