The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with approximately 1.3 billion baptised Catholics worldwide as of 2017. As the world's "oldest continuously functioning international institution", it has played a prominent role in the history and development of Western civilisation. The church is headed by the Bishop of Rome, known as the Pope. Its central administration, the Holy See, is in the Vatican City, an enclave within the city of Rome in Italy.
Catholic theology is based on the Nicene Creed. The Catholic Church teaches that it is the One, Holy, Catholic and Apostolic church founded by Jesus Christ, 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, reserving infallibility, passed down by sacred tradition. The Latin Church, the twenty-three Eastern Catholic Churches, and institutes such as mendicant orders and enclosed monastic 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 in the Catholic Church as Mother of God and Queen of Heaven, honoured in dogmas and devotions. Its teaching includes sanctification through faith and evangelisation of the Gospel as well as Catholic social teaching, which emphasises voluntary support for the sick, the poor, and the afflicted through the corporal and spiritual works of mercy. The Catholic Church is the largest non-government provider of education and health care in the world.
The Catholic Church has influenced Western philosophy, culture, science, and art. Catholics live all over the world through missions, diaspora, and conversions. Since the 20th century the majority reside in the southern hemisphere 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, as well as with the Oriental Orthodox churches prior to the Chalcedonian schism in 451 over differences in Christology. The Reformation of the 16th century resulted in Protestants breaking away.
From the late 20th century, the Catholic Church has been criticised for its doctrines on sexuality, its refusal to ordain women, as well as the handling of sexual abuse cases involving clergy.