The Roman Catholic Church traces its origins back to the apostles, with the Bishop of Rome (the Pope) considered the successor of Peter. It became the dominant religious institution in Western Europe after the fall of the Roman Empire. Catholic doctrine emphasizes both Scripture and Tradition as authoritative, salvation through faith and works, and the seven sacraments, including baptism, Eucharist, confirmation, confession, marriage, holy orders, and anointing of the sick. The Eucharist is considered the real presence of Christ, and the Pope serves as the supreme earthly authority. Historically, the Church played a central role in European politics and society, experienced the Great Schism with the Eastern churches in 1054, and faced the Protestant Reformation in the 16th century. Vatican II (1962–1965) modernized aspects of worship and encouraged engagement with contemporary society. Today, the Catholic Church has about 1.3 billion members worldwide. It maintains social conservatism on issues like abortion, same-sex marriage, and women’s ordination, while engaging globally in education, healthcare, and social justice.

The Eastern Orthodox Church shares common roots with Catholicism but formally split in the Great Schism of 1054 over papal authority, cultural differences, and theological disputes such as the Filioque clause. Eastern Orthodox theology emphasizes Scripture and Holy Tradition as equally important, salvation as theosis (union with God), and seven sacraments with the Eucharist central to worship. Unlike the Catholic Church, it rejects papal supremacy, favoring conciliar leadership with bishops and patriarchs considered equals. The Eastern Orthodox Church is known for its use of icons, highly ritualized and mystical liturgy, and clerical structure in which priests may marry before ordination, while bishops remain celibate. Today, it has about 220–260 million members worldwide, organized into national churches such as Greek, Russian, and Serbian Orthodox, primarily in Eastern Europe, Russia, and the Middle East.

The Oriental Orthodox Churches split from both Catholic and Eastern Orthodox bodies after the Council of Chalcedon in 451 AD due to disagreements over Christology, particularly how Christ’s divine and human natures coexist. Oriental Orthodox theology is similar to Eastern Orthodoxy regarding sacraments, liturgy, and tradition but adheres to Miaphysitism, teaching that Christ’s divine and human natures are united in one nature. Major Oriental Orthodox bodies include the Coptic Orthodox Church (Egypt), Armenian Apostolic Church, Ethiopian Orthodox Church, Syriac Orthodox Church, Eritrean Orthodox Church, and the Malankara Orthodox Church (India). Today, these churches have around 60 million members worldwide and are known for their ancient liturgies, monastic traditions, and cultural distinctiveness, often facing historical and contemporary persecution in their regions.