The pope (Latin: papa from Greek: πάππας pappas, a child's word for "father"), also known as the supreme pontiff (from Latin pontifex maximus "greatest priest"), is the Bishop of Rome and therefore ex officio the leader of the worldwide Catholic Church. The primacy of the Roman bishop is largely derived from his role as the supposed apostolic successor to Saint Peter, to whom Jesus is said to have given the Keys of Heaven and the powers of "binding and loosing", naming him as the "rock" upon which the church would be built. Since the 1860s, the pope has also been head of state of Vatican City, a sovereign city-state entirely enclaved within Rome, Italy. The current pope is Francis, who was elected on 13 March 2013, succeeding Benedict XVI.
The office of the pope is the papacy. His ecclesiastical jurisdiction, the Diocese of Rome, is often called the "Holy See" or the "Apostolic See", the latter name being based on the belief that the Bishop of Rome is the apostolic successor to Saint Peter. The pope is considered one of the world's most powerful people because of his extensive diplomatic and cultural influence.
The papacy is one of the most enduring institutions in the world and has had a prominent part in world 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. Currently, in addition to the expansion of the Christian faith and doctrine, the popes are involved in ecumenism and interfaith dialogue, charitable work, and the defense of human rights.
In some periods of history, popes, who originally had no temporal powers, accrued wide secular powers rivalling those of temporal rulers. However, in recent centuries the temporal authority of the papacy has declined and the office is now almost exclusively 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 word pope derives from Greek πάππας meaning "father". In the early centuries of Christianity, this title was applied, especially in the east, to all bishops and other senior clergy, and later became reserved in the west to the Bishop of Rome, a reservation made official only in the 11th century. The earliest record of the use of this title was in regard to the by then deceased Patriarch of Alexandria, Pope Heraclas of Alexandria (232–248). The earliest recorded use of the title "pope" in English dates to the mid-10th century, when it was used in reference to Pope Vitalian in an Old English translation of Bede's Historia ecclesiastica gentis Anglorum.
The Catholic Church teaches that the pastoral office, the office of shepherding the Church, that was held by the apostles, as a group or "college" with Saint Peter as their head, is now held by their successors, the bishops, with the bishop of Rome (the pope) as their head. Thus, is derived another title by which the pope is known, that of "Supreme Pontiff".
The Catholic Church teaches that Jesus personally appointed Peter as leader of the Church, and the Catholic Church's dogmatic constitution Lumen gentium makes a clear distinction between apostles and bishops, presenting the latter as the successors of the former, with the pope as successor of Peter, in that he is head of the bishops as Peter was head of the apostles. Some historians argue against the notion that Peter was the first bishop of Rome, noting that the episcopal see in Rome can be traced back no earlier than the third century. The writings of the Church Father Irenaeus who wrote around AD 180 reflect a belief that Peter "founded and organized" the Church at Rome. Moreover, Irenaeus was not the first to write of Peter's presence in the early Roman Church. Clement of Rome wrote in a letter to the Corinthians, c. 96, about the persecution of Christians in Rome as the "struggles in our time" and presented to the Corinthians its heroes, "first, the greatest and most just columns", the "good apostles" Peter and Paul. St. Ignatius of Antioch wrote shortly after Clement and in his letter from the city of Smyrna to the Romans he said he would not command them as Peter and Paul did. Given this and other evidence, such as Emperor Constantine's erection of the "Old St. Peter's Basilica" on the location of St. Peter's tomb, as held and given to him by Rome's Christian community, many scholars agree that Peter was martyred in Rome under Nero, although some scholars argue that he may have been martyred in Palestine.