What is the largest religion in the world by number of adherents?

The largest religion in the world by number of adherents is Christianity. Recent global estimates place the number of Christians at roughly 2.3 billion, or about 28.8% of the world’s population, putting Christianity ahead of Islam, Hinduism and Buddhism.

Christianity began in the 1st century CE in the eastern Mediterranean and is based on the life, teachings, death and resurrection of Jesus of Nazareth. It grew out of the Jewish tradition and spread widely through the Roman Empire, later expanding around the world through missionary activity, migration, trade and colonial-era networks.

The Christian population is not a single uniform community. Its largest traditions include Catholicism, Protestantism and Eastern Orthodoxy, alongside Oriental Orthodox churches and many other denominations. Catholicism is the largest individual Christian tradition, while Protestant Christianity includes thousands of denominations and movements.

A common source of confusion is Islam’s rapid population growth. Islam is generally considered the world’s second-largest religion, with around 2.0 billion adherents, and demographic projections suggest the gap may narrow substantially. Those projections do not change Christianity’s current position as the largest religion by population.