Four Marks of the Church in the context of "Catholic Christian"

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.

The expression "one true church" refers to an ecclesiological position asserting that Jesus gave his authority in the Great Commission solely to a particular visible Christian institutional church—what is commonly called a denomination. This view is maintained by the Catholic Church, the Eastern Orthodox Church, the Oriental Orthodox communion, the Assyrian Church of the East, the Ancient Church of the East, and the Lutheran churches, as well as certain Baptists. Each of them maintains that their own specific institutional church (denomination) exclusively represents the one and only original church. The claim to the title of the "one true church" relates to the first of the Four Marks of the Church mentioned in the Nicene Creed: "one, holy, catholic, and apostolic church". As such, it also relates to claims of both catholicity and apostolic succession: asserting inheritance of the spiritual, ecclesiastical and sacramental authority and responsibility that Jesus Christ gave to the apostles.

The concept of schism somewhat moderates the competing claims between some churches—one can potentially repair schism, since they are striving for the same goal. For example, the Catholic and Eastern Orthodox churches each regard the other as schismatic and at very least heterodox, if not heretical, yet both have held dialogues and even partaken in Councils in attempts to resolve the division that exists between them.

Catholicity (from Ancient Greek: καθολικός, romanized: katholikós, lit. 'general', 'universal', via Latin: catholicus) is a concept pertaining to beliefs and practices that are widely accepted by numerous Christian denominations, most notably by those Christian denominations that describe themselves as catholic in accordance with the Four Marks of the Church, as expressed in the Nicene Creed formulated at the First Council of Constantinople in 381: "[I believe] in one, holy, catholic, and apostolic Church." The English adjective catholic is derived from the Ancient Greek adjective καθολικός (romanized: katholikos), meaning "general", "universal". Thus, "catholic" means that in the Church the wholeness of the Christian faith, full and complete, all-embracing, and with nothing lacking, is proclaimed to all people without excluding any part of the faith or any class or group of people. An early definition for what is "catholic" was summarized in what is known as the Vincentian Canon in the 5th century Commonitory: "what has been believed everywhere, always, and by all."

This is distinct from the capitalized word Catholic, referring specifically to the Catholic Church and often, further, the Roman Catholic Church, used especially in ecumenical contexts and in countries where other churches use the term catholic, to distinguish it from broader meanings of the term. Though the community led by the pope in Rome is known as the Catholic Church, the traits of catholicity, and thus the term catholic, are also ascribed to denominations such as the Eastern Orthodox Church, the Oriental Orthodox Church, and the Assyrian Church of the East. It also occurs in the language of churches that decisively split from the Roman Catholic Church, like Lutheranism and Anglicanism, as well as Independent Catholicism, Old Catholicism and other Christian denominations. While traits used to define catholicity, as well as recognition of these traits in other denominations, vary among these groups, such attributes include formal sacraments, an episcopal polity, apostolic succession, highly structured liturgical worship, and other shared Ecclesiology.