Pope Benedict XVI (Latin: Benedictus XVI; Italian: Benedetto XVI; German: Benedikt XVI.; born Joseph Aloisius Ratzinger, German: [jozf alzis ats], on 16 April 1927) is a retired prelate of the Catholic church who served as the head of the church and the sovereign of the Vatican city state from 2005 until his resignation in 2013. Benedict's election as pope occurred in the 2005 papal conclave that followed the death of Pope John Paul II. Benedict chose to be known by the title "pope emeritus" upon his resignation.Ordained as a priest in 1951 in his native Bavaria, Ratzinger embarked on an academic career and established himself as a highly regarded theologian by the late 1950s. He was appointed a full professor in 1958 at the age of 31. After a long career as a professor of theology at several German universities, he was appointed Archbishop of Munich and Freising and created a cardinal by Pope Paul VI in 1977, an unusual promotion for someone with little pastoral experience. In 1981, he was appointed Prefect of the Congregation for the Doctrine of the Faith, one of the most important dicasteries of the Roman Curia. From 2002 until his election as pope, he was also Dean of the College of Cardinals. Prior to becoming pope, he was "a major figure on the Vatican stage for a quarter of a century"; he had an influence "second to none when it came to setting church priorities and directions" as one of John Paul II's closest confidants. He has lived in Rome since 1981.

His prolific writings generally defend traditional Catholic doctrine and values. He was originally a liberal theologian, but adopted conservative views after 1968. During his papacy, Benedict XVI advocated a return to fundamental Christian values to counter the increased secularisation of many Western countries. He views relativism's denial of objective truth, and the denial of moral truths in particular, as the central problem of the 21st century. He taught the importance of both the Catholic Church and an understanding of God's redemptive love. Benedict also revived a number of traditions, including elevating the Tridentine Mass to a more prominent position. He strengthened the relationship between the Catholic Church and art, promoted the use of Latin, and reintroduced traditional papal vestments, for which reason he was called "the pope of aesthetics". He has been described as "the main intellectual force in the Church" since the mid-1980s.On 11 February 2013, Benedict unexpectedly announced his resignation in a speech in Latin before the cardinals, citing a "lack of strength of mind and body" due to his advanced age. His resignation became effective on 28 February 2013. He is the first pope to resign since Gregory XII in 1415, and the first to do so on his own initiative since Celestine V in 1294. As pope emeritus, Benedict retains the style of His Holiness and continues to dress in the papal colour of white. He was succeeded by Francis on 13 March 2013, and he moved into the newly renovated Mater Ecclesiae Monastery in the Vatican for his retirement on 2 May 2013. In his retirement, Benedict XVI has made occasional public appearances alongside Francis.

In addition to his native German language, Benedict has some level of proficiency with French, Italian, English, Latin, and Spanish, and can read Ancient Greek and Biblical Hebrew. He is a member of several social science academies, such as the French Acadmie des Sciences Morales et Politiques. He plays the piano and has a preference for Mozart and Bach.On 4 September 2020, Benedict became the longest-lived person to have held the office of pope, at 93 years, 4 months, 16 days, surpassing Leo XIII, who died in 1903.

The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.3 billion baptised Catholics worldwide as of 2019. As the world's oldest and largest continuously functioning international institution, it has played a prominent role in the history and development of Western civilisation. The church consists of 24 particular churches and almost 3,500 dioceses and eparchies around the world. The pope, who is the bishop of Rome, is the chief pastor of the church. The bishopric of Rome, known as the Holy See, is the central governing authority of the church. The administrative body of the Holy See, the Roman Curia, has its principal offices in Vatican City, a small enclave of Rome, of which the pope is head of state.

The core beliefs of Catholicism are found in the Nicene Creed. The Catholic Church teaches that it is the one, holy, catholic and apostolic church founded by Jesus Christ in his Great Commission, that its bishops are the successors of Christ's apostles, and that the pope is the successor to Saint Peter, upon whom primacy was conferred by Jesus Christ. It maintains that it practises the original Christian faith taught by the apostles, preserving the faith infallibly through scripture and sacred tradition as authentically interpreted through the magisterium of the church. The Latin Church, the twenty-three Eastern Catholic Churches, and institutes such as mendicant orders, enclosed monastic orders and third orders reflect a variety of theological and spiritual emphases in the church.Of its seven sacraments, the Eucharist is the principal one, celebrated liturgically in the Mass. The church teaches that through consecration by a priest, the sacrificial bread and wine become the body and blood of Christ. The Virgin Mary is venerated as the Perpetual Virgin, Mother of God, and Queen of Heaven; she is honoured in dogmas and devotions. Catholic social teaching emphasises voluntary support for the sick, the poor, and the afflicted through the corporal and spiritual works of mercy. The Catholic Church operates thousands of Catholic schools, hospitals, and orphanages around the world, and is the largest non-government provider of education and health care in the world. Among its other social services are numerous charitable and humanitarian organisations.

The Catholic Church has profoundly influenced Western philosophy, culture, art, music and science. Catholics live all over the world through missions, diaspora, and conversions. Since the 20th century, the majority have resided in the southern hemisphere, partially due to secularisation in Europe and increased persecution in the Middle East. The Catholic Church shared communion with the Eastern Orthodox Church until the East–West Schism in 1054, disputing particularly the authority of the pope. Before the Council of Ephesus in AD 431, the Church of the East also shared in this communion, as did the Oriental Orthodox Churches before the Council of Chalcedon in AD 451; all separated primarily over differences in Christology. In the 16th century, the Reformation led to Protestantism also breaking away. From the late 20th century, the Catholic Church has been criticised for its teachings on sexuality, its doctrine against ordaining women, and its handling of sexual abuse cases involving clergy.