A papal conclave is a meeting of the College of Cardinals convened, during a period of vacancy in the papal office, to elect a Bishop of Rome who then becomes the Pope. The Pope is considered by Roman Catholics to be the apostolic successor of Saint Peter and earthly head of the Roman Catholic Church. The conclave, the means and process for choosing the pope for little more than half of the time the church has been in existence, is now the oldest ongoing method for choosing the leader of an institution.

A history of political interference in these elections and consequently long vacancies between popes, and most immediately the interregnum of 1268–1271, prompted the Second Council of Lyons to decree in 1274 that the electors should be locked in seclusion cum clave (Latin for "with a key"), and not permitted to leave until a new Bishop of Rome had been elected. Conclaves are now held in the Sistine Chapel in the Palace of the Vatican.

Since the Apostolic Age, the Bishop of Rome (like other bishops) was chosen by the consensus of the clergy and people of Rome. The body of electors was more precisely defined when, in 1059, the College of Cardinals was designated the sole body of electors. Since then other details of the process have developed. In 1970, Pope Paul VI limited the electors to cardinals under 80 years of age. The Pope may change the procedures for electing his successor; the current^[update] procedures were established by Pope John Paul II in his constitution Universi Dominici Gregis and amended by a motu proprio of Pope Benedict XVI dated 11 June 2007. A two-thirds vote of the electorate is required to elect the new pope.