Primus inter pares in the context of "Holy Roman Emperor"

The Eastern Orthodox Church, officially the Orthodox Catholic Church, and also called the Greek Orthodox Church or simply the Orthodox Church, is one of the three major doctrinal and jurisdictional groups of Christianity. As of 2012, it has approximately 300 million adherents and is the third largest religious community in the world after Catholics and Sunni Muslims. The Eastern Orthodox Church operates as a communion of autocephalous churches, each governed by its bishops via local synods. The church has no central doctrinal or governmental authority analogous to the pope of the Catholic Church. Nevertheless, the Ecumenical Patriarch of Constantinople is recognised by them as primus inter pares ('first among equals'), a title held by the patriarch of Rome prior to 1054. As one of the oldest surviving religious institutions in the world, the Eastern Orthodox Church has played an especially prominent role in the history and culture of Eastern and Southeastern Europe. Since 2018, there has been an ongoing schism between Constantinople and Moscow, with the two not in full communion with each other.

Eastern Orthodox theology is based on the Scriptures and holy tradition, which incorporates the dogmatic decrees of the seven ecumenical councils, and the teaching of the Church Fathers. The church teaches that it is the one, holy, catholic and apostolic church established by Jesus Christ in his Great Commission, and that its bishops are the successors of Christ's apostles. It maintains that it practises the original Christian faith, as passed down by holy tradition. Its patriarchates, descending from the pentarchy, and other autocephalous and autonomous churches, reflect a variety of hierarchical organisation. It recognises seven major sacraments (which are called holy mysteries), of which the Eucharist is the principal one, celebrated liturgically in synaxis. The church teaches that through consecration invoked by a priest, the sacrificial bread and wine become the body and blood of Christ. The Virgin Mary is venerated in the Eastern Orthodox Church as the Theotokos, which means 'God-bearer', and she is honoured in devotions.

The Ecumenical Patriarchate of Constantinople (Greek: Οἰκουμενικὸν Πατριαρχεῖον Κωνσταντινουπόλεως, romanized: Oikoumenikón Patriarkhíon Konstantinoupóleos, IPA: [ikumeniˈkon patriarˈçion konstandinuˈpoleos]; Latin: Patriarchatus Oecumenicus Constantinopolitanus; Turkish: Rum Ortodoks Patrikhanesi, İstanbul Ekümenik Patrikhanesi, "Roman Orthodox Patriarchate, Ecumenical Patriarchate of Istanbul") is one of the fifteen to seventeen autocephalous churches that together compose the Eastern Orthodox Church. It is headed by the Ecumenical Patriarch of Constantinople.

Because of its historical location as the capital of the former Eastern Roman Empire and its role as the mother church of most modern Eastern Orthodox churches, Constantinople holds a special place of honor within Eastern Orthodox Christianity and serves as the seat for the Ecumenical Patriarch, who enjoys the status of primus inter pares (first among equals) among the world's Eastern Orthodox prelates and is regarded as the representative and spiritual leader of Eastern Orthodox Christians. Phanar (Turkish: Fener), the name of the neighbourhood where ecumenical patriarch resides, is often used as a metaphor or shorthand for the Ecumenical Patriarchate of Constantinople.

The Ecumenical Patriarch of Constantinople (Greek: Οἰκουμενικός Πατριάρχης, romanized: Oikoumenikós Patriárchēs) is the archbishop of Constantinople and primus inter pares (first among equals) among the heads of the several autocephalous churches that comprise the Eastern Orthodox Church. The ecumenical patriarch is regarded as the representative and spiritual leader of the Eastern Orthodox Christians worldwide. The term ecumenical in the title is a historical reference to the Ecumene, a Greek designation for the civilised world, i.e. the Roman Empire, and it stems from Canon 28 of the Council of Chalcedon.

The patriarch's see, the Ecumenical Patriarchate of Constantinople, is one of the most enduring institutions in the world and has had a prominent part in world history. The ecumenical patriarchs in ancient times helped in the spread of Christianity and the resolution of various doctrinal disputes. In the Middle Ages, they played a major role in the affairs of the Eastern Orthodox Church, as well as in the politics of the Orthodox world, and in spreading Christianity among the Slavs. Currently, in addition to the expansion of the Christian faith and the Eastern Orthodox doctrine, the patriarchs are involved in ecumenism and interfaith dialogue, charitable work, and the defense of Orthodox Christian traditions.

Papal primacy, also known as the primacy of the bishop of Rome, is an ecclesiological doctrine in the Catholic Church concerning the respect and authority that is due to the pope from other bishops and their episcopal sees. While the doctrine is accepted at a fundamental level by both the Catholic Church (Eastern and Western) and the Eastern Orthodox Church, the two disagree on the nature of primacy.

English academic and Catholic priest Aidan Nichols wrote that "at root, only one issue of substance divides the Eastern Orthodox and the Catholic Churches, and that is the issue of the primacy." French Eastern Orthodox researcher Jean-Claude Larchet wrote that, together with the Filioque controversy, differences in interpretation of this doctrine have been and remain the primary causes of schism between the Catholic Church and the Eastern Orthodox Church. In the Eastern Orthodox churches, some understand the primacy of the bishop of Rome to be merely one of greater honour, regarding him as primus inter pares ("first among equals"), without effective power over other churches. A prominent 20th century Eastern Orthodox Christian theologian, Fr. Alexander Schmemann, envisioned a primacy that sums up rather than rules over: "Primacy is power, but as power it is not different from the power of a bishop in each church. It is not a higher power but indeed the same power, only expressed, manifested, and realized by one."

The Anglican Communion (AC) is a Christian communion consisting of the autocephalous national and regional churches historically in full communion with the archbishop of Canterbury in England, who has acted as a focus of unity, recognised as primus inter pares ("first among equals"), but without formal authority in Anglican provinces outside of the Church of England. Most, but not all, member churches of the communion are the historic national or regional Anglican churches.

With approximately 85–110 million members in 2025, among its 47 member churches, it is the third or fourth largest Christian communion of churches globally, after the Catholic, Eastern Orthodox, and, possibly, World Communion of Reformed Churches. The Anglican Communion considers baptism to be "the traditional gauge" or definition for membership.

Anglicanism, also known as Episcopalianism in some countries, is a Western Christian tradition which developed from the practices, liturgy, and identity of the Church of England following the English Reformation, in the context of the Protestant Reformation in Europe. It is one of the largest branches of Christianity, with around 110 million adherents within the Anglican Communion, and more than 400,000 outside of the Anglican Communion, worldwide as of 2025.

Adherents of Anglicanism are called Anglicans; they are also called Episcopalians in some countries. Most are members of national or regional ecclesiastical provinces of the international Anglican Communion, one of the largest Christian bodies in the world, and the world's third-largest Christian communion. The provinces within the Anglican Communion have historically been in full communion with the See of Canterbury and thus with the archbishop of Canterbury, whom the communion refers to as its primus inter pares (Latin, 'first among equals'). The archbishop calls the decennial Lambeth Conference, chairs the meeting of primates, and is the president of the Anglican Consultative Council. Some churches that are not part of the Anglican Communion or recognised by it also call themselves Anglican, including those that are within the Continuing Anglican movement and Anglican realignment.