The Pope (Latin: Papa, from Greek: πάππας, romanized: Páppas, lit. 'father'), also known as supreme pontiff (pontifex maximus or summus pontifex), Roman pontiff (Romanus pontifex) or sovereign pontiff, is the bishop of Rome (or historically the patriarch of Rome), head of the worldwide Catholic Church, and has also served as the head of state or sovereign of the Papal States and later the Vatican City State since the eighth century. 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 Francis, who was elected on 13 March 2013.

While his office is called the papacy, the jurisdiction of the episcopal see is called the Holy See. It is the Holy See that is the sovereign entity by international law headquartered in the distinctively independent Vatican City State, a city-state which forms a geographical enclave within the conurbation of Rome, established by the Lateran Treaty in 1929 between Italy and the Holy See to ensure its temporal 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.

According to Catholic tradition, the apostolic see of Rome was founded by Saint Peter and Saint Paul in the first century. The papacy is one of the most enduring institutions in the world and has had a prominent part in human history. In ancient times, the popes helped spread Christianity and intervened to find resolutions in various doctrinal disputes. In the Middle Ages, they played a role of secular importance in Western Europe, often acting as arbitrators between Christian monarchs. In addition to the expansion of Christian faith and doctrine, modern popes are involved in ecumenism and interfaith dialogue, charitable work, and the defense of human rights.

Over time, the papacy accrued broad secular and political influence, eventually rivaling those of territorial rulers. In recent centuries, the temporal authority of the papacy has declined and the office is now largely focused on religious matters. By contrast, papal claims of spiritual authority have been increasingly firmly expressed over time, culminating in 1870 with the proclamation of the dogma of papal infallibility for rare occasions when the pope speaks ex cathedra—literally "from the chair (of Saint Peter)"—to issue a formal definition of faith or morals. The pope is considered one of the world's most powerful people due to the extensive diplomatic, cultural, and spiritual influence of his position on both 1.3 billion Catholics and those outside the Catholic faith, and because he heads the world's largest non-government provider of education and health care, with a vast network of charities.