Cardinal Joseph Ratzinger is inaugurated as the 265th Pope of the Catholic Church taking the name Pope Benedict XVI.

A cardinal is a senior member of the clergy of the Catholic Church. As titular members of the clergy of the Diocese of Rome, they serve as advisors to the pope, who is the bishop of Rome and the visible head of the worldwide Catholic Church. Cardinals are chosen and formally created by the pope, and typically hold the title for life. Collectively, they constitute the College of Cardinals. The most solemn responsibility of the cardinals is to elect a new pope in a conclave, almost always from among themselves, with a few historical exceptions, when the Holy See is vacant.

Papal inauguration is a liturgical service of the Catholic Church within Mass celebrated in the Roman Rite but with elements of Byzantine Rite for the ecclesiastical investiture of a pope. Since the inauguration of Pope John Paul I, it has not included the 820-year-old (1143–1963) papal coronation ceremony.

The pope is the bishop of Rome and the visible head of the worldwide Catholic Church. He is also known as the supreme pontiff, Roman pontiff, or sovereign pontiff. From the 8th century until 1870, the pope was the sovereign or head of state of the Papal States, and since 1929 of the much smaller Vatican City state. 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 Leo XIV, who was elected on 8 May 2025 on the second day of the 2025 papal conclave.

The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.27 to 1.41 billion baptized Catholics worldwide as of 2025. It is among the world's oldest and largest international institutions and has played a prominent role in the history and development of Western civilization. The Church consists of 24 sui iuris (autonomous) churches, including the Latin Church and 23 Eastern Catholic Churches, which comprise almost 3,500 dioceses and eparchies around the world, each overseen by one or more bishops. The pope, who is the bishop of Rome, is the chief pastor of the church.