Papal supremacy in the context of "East–West Schism"

The Catholic Church (Latin: Ecclesia Catholica), also known as the Roman Catholic Church, is the largest Christian church, with 1.27 to 1.41 billion baptized Catholics worldwide as of 2025. 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 (autonomous) churches, including the Latin Church and 23 Eastern Catholic Churches, which comprise almost 3,500 dioceses and eparchies around the world, each overseen by one or more bishops. The pope, who is the bishop of Rome, is the chief pastor of the church.

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 of 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 or teaching office of the church. The Roman Rite and others of the Latin Church, the Eastern Catholic liturgies, and communities and societies such as mendicant orders, enclosed monastic orders, third orders and voluntary charitable lay associations reflect a variety of theological and spiritual emphases in the church.

A Christian denomination is a distinct religious body within Christianity, identified by traits such as a name, organization and doctrine. Individual bodies, however, may use alternative terms to describe themselves, such as church, convention, communion, assembly, house, union, network, or sometimes fellowship. Divisions between one denomination and another are primarily defined by authority and doctrine. Issues regarding the nature of Jesus, Trinitarianism, salvation, the authority of apostolic succession, eschatology, conciliarity, papal supremacy and papal primacy among others may separate one denomination from another. Groups of denominations, often sharing broadly similar beliefs, practices, and historical ties—can be known as "branches of Christianity" or "denominational families" (e.g. Eastern or Western Christianity and their sub-branches). These "denominational families" are often imprecisely also called denominations.

Christian denominations since the 20th century have often involved themselves in ecumenism. Ecumenism refers to efforts among Christian bodies to develop better understandings and closer relationships. It also refers to efforts toward visible unity in the Christian Church, though the terms of visible unity vary for each denomination of Christianity, as certain groups teach they are the one true church, or that they were divinely instituted for the propagation of a certain doctrine. The largest ecumenical organization in Christianity is the World Council of Churches.

The terms Old Catholic Church, Old Catholics, Old-Catholic churches, or Old Catholic movement, designate "any of the groups of Western Christians who believe themselves to maintain in complete loyalty the doctrine and traditions of the undivided church but who separated from the See of Rome after the First Vatican Council of 1869–70".

The expression Old Catholic has been used from the 1850s by communions separated from the Roman Catholic Church over certain doctrines, primarily concerned with papal authority and infallibility. Some of these groups, especially in the Netherlands, had already existed long before the term. The Old Catholic Church is separate and distinct from Traditionalist Catholicism.

The Council of Florence is the seventeenth ecumenical council recognized by the Catholic Church, held between 1431 and 1445. It was convened in territories under the Holy Roman Empire. Italy became a venue of a Catholic ecumenical council after a gap of about 2 centuries (the last ecumenical council to be held in Italy was the 4th Council of the Lateran in Rome's Lateran Palace). It was convoked in Basel as the Council of Basel by Pope Martin V shortly before his death in February 1431 and took place in the context of the Hussite Wars in Bohemia and the rise of the Ottoman Empire. At stake was the greater conflict between the conciliar movement and the principle of papal supremacy.

The Council entered a second phase after Emperor Sigismund's death in 1437. Pope Eugene IV translated the Council to Ferrara on 8 January 1438, where it became the Council of Ferrara and succeeded in drawing some of the Byzantine ambassadors who were in attendance at Basel to Italy. Some Council members rejected the papal decree and remained at Basel: this rump Council suspended Eugene, declared him a heretic, and then in November 1439 elected an antipope, Felix V.