The history of Christianity begins with Jesus, an itinerant Jewish preacher and teacher, who was crucified in Jerusalem c. AD 30–33. His followers proclaimed that he was the incarnation of God and had risen from the dead. In the two millennia since, Christianity has spread across the world, becoming the world’s largest religion with over two billion adherents worldwide.

Initially, Christianity was a mostly urban grassroots movement. Its religious text was written in the first century. A formal church government developed, and it grew to over a million adherents by the third century. Constantine the Great issued the Edict of Milan legalizing it in 315. Christian art, architecture, and literature blossomed during the fourth century, but competing theological doctrines led to divisions. The Nicene Creed of 325, the Nestorian schism, the Church of the East and Oriental Orthodoxy resulted. While the Western Roman Empire ended in 476, its successor states and its eastern compatriot—the Byzantine Empire—remained Christian.

After the fall of Rome in 476, western monks preserved culture and provided social services. Early Muslim conquests devastated many Christian communities in the Middle East and North Africa, but Christianization continued in Europe and Asia and helped form the states of Eastern Europe. The 1054 East–West Schism saw the Byzantine Empire’s Eastern Orthodoxy and Western Europe’s Catholic Church separate. In spite of differences, the East requested western military aid against the Turks, resulting in the Crusades. Gregorian reform led to a more centralized and bureaucratic Catholicism. Faced with internal and external challenges, the church fought heresy and established courts of inquisition. Artistic and intellectual advances among western monks played a part in the Renaissance and the later Scientific Revolution.

In the 14th century, the Western Schism and several European crises led to the 16th-century Reformation when Protestantism formed. Reformation Protestants advocated for religious tolerance and the separation of church and state and impacted economics. Quarrelling royal houses took sides precipitating the European wars of religion. Christianity spread with the colonization of the Americas, Australia, and New Zealand. Different parts of Christianity influenced the Age of Enlightenment, American and French Revolutions, the Industrial Revolution, and the Atlantic slave trade. Some Protestants created biblical criticism while others responded to rationalism with Pietism and religious revivals that created new denominations. Nineteenth century missionaries laid the linguistic and cultural foundation for many nations.

In the twentieth century, Christianity declined in most of the Western world but grew in the Global South, particularly Southeast Asia and Sub-Saharan Africa. In the twenty first century, Christianity has become the most diverse and pluralistic of the world’s religions embracing over 3000 of the world’s languages.

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