The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.3 billion baptized Catholics worldwide as of 2019. 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 churches, including the Latin Church and 23 Eastern Catholic Churches, which comprise almost 3,500 dioceses and eparchies located 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 the Italian city 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 Roman Rite and others of the Latin Church, the Eastern Catholic liturgies, 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 emphasizes 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, universities and colleges, 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 organizations.

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 secularization 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. The Eastern Catholic Churches, who have a combined membership of approximately 18 million, represent a body of Eastern Christians who returned or remained in communion with the pope during or following these schisms for a variety of historical circumstances. In the 16th century, the Reformation led to Protestantism also breaking away. From the late 20th century, the Catholic Church has been criticized for its teachings on sexuality, its doctrine against ordaining women, and its handling of sexual abuse cases involving clergy.