The Oriental Orthodox communion is composed of six autocephalous churches: the Coptic Orthodox Church of Alexandria, the Syriac Orthodox Church of Antioch, the Armenian Apostolic Church, the Ethiopian Orthodox Tewahedo Church, the Eritrean Orthodox Tewahedo Church, and the Malankara Orthodox Syrian Church. Collectively, they consider themselves to be the One, Holy, Catholic, and Apostolic church founded by Jesus Christ in his Great Commission, and that its bishops are the successors of Christ's apostles. Most member churches are part of the World Council of Churches. All member churches share a virtually identical theology, with the distinguishing feature being Miaphysitism. Three very different rites are practiced in the communion: the western-influenced Armenian Rite, the West Syrian Rite of the two Syriac churches, and the Alexandrian Rite of the Copts, Ethiopians and Eritreans.
Prior to the Council of Chalcedon in 451 AD, the Oriental Orthodox churches shared in this communion with the contemporary Roman Catholic Church, and Eastern Orthodox Church, separating primarily over differences in Christology. Subsequent to this event, Oriental Orthodoxy developed distinctively under the patriarchate of Alexandria in Egypt, originally part of the Pentarchy, and the only episcopal see besides the Holy See to maintain the title "Pope". Its Syriac Orthodox patriarchate member church was recognised as authority among part of the Saint Thomas Christians in India, retained until this day.
The majority of Oriental Orthodox Christians live in Egypt, Ethiopia, Eritrea, and Armenia, with smaller Syriac communities living in the Middle East – decreasing due to persecution – and India. There are also many in other parts of the world, formed through diaspora, conversions, and missionary activity.
The Oriental Orthodox churches are distinguished by their recognition of only the first three ecumenical councils during the period of the state church of the Roman Empire – the First Council of Nicaea in 325, the First Council of Constantinople in 381 and the Council of Ephesus in 431. Oriental Orthodoxy shares much theology and many ecclesiastical traditions with the Eastern Orthodox Church; these include a similar doctrine of salvation and a tradition of collegiality between bishops, as well as reverence of the Theotokos and use of the Nicene creed.
The primary theological difference between the two communions is the differing Christology. Oriental Orthodoxy rejects the Chalcedonian Definition, and instead adopts the Miaphysite formula, believing that the human and divine natures of Christ are united. Historically, the early prelates of the Oriental Orthodox churches thought that the Chalcedonian Definition implied a possible repudiation of the Trinity or a concession to Nestorianism.