With an area of 49 hectares (121 acres) and as of 2023 a population of about 764, it is the smallest state in the world both by area and by population. 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. 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 Vatican is also a metonym for the Holy See.

The Holy See dates back to early Christianity and is the principal episcopal see of the Catholic Church, which has approximately 1.329 billion baptised Catholics in the world as of 2018 in the Latin Church and 23 Eastern Catholic Churches. The independent state of Vatican City, on the other hand, came into existence on 11 February 1929 by the Lateran Treaty between the Holy See and 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.

Vatican City contains religious and cultural sites such as St. Peter's Basilica, the Sistine Chapel, the Vatican Apostolic Library, and the Vatican Museums. They feature some of the world's most famous paintings and sculptures. The unique economy of Vatican City is supported financially by donations from the faithful, by the sale of postage stamps and souvenirs, fees for admission to museums, and sales of publications. Vatican City has no taxes, and items are duty-free.