A sacerdotal state is a state whose head is also an ecclesiastical leader designated by a religious body. An example of this kind of state is the Vatican City - its heads of state, the popes of the Catholic Church, have governed papal lands distinct from secular authority since the eighth century CE. Andorra operates under a semi-sacerdotal system, as one of its co-heads of state is the bishop of Urgell, while the other is the president of France. However unlike the Vatican, the co-princes of Andorra are not closely involved in the government.

Vatican City, officially the Vatican City State, is a landlocked sovereign country, city-state, microstate, and enclave within Rome, Italy. It became independent from Italy in 1929 with the Lateran Treaty, and it is a distinct territory under "full ownership, exclusive dominion, and sovereign authority and jurisdiction" of the Holy See, itself a sovereign entity under international law, which maintains the city-state's temporal power and governance, diplomatic, and spiritual independence. The Vatican is also a metonym for the pope, Holy See, and Roman Curia.