Worlds Largest Religion 2025. Christianity, with about 2.38 billion followers, is the world's largest religion, deeply diversified into numerous denominations like catholicism, protestantism, and eastern orthodoxy. Christianity is the largest religion in the world.

Islam is forecast to be the world’s largest. In relative terms islam is doing well, becoming the fastest growing religion in both china and india (the world’s two most populous countries) and russia and canada (the.