High Quality Content by WIKIPEDIA articles! As of the early 21st century, Christianity has around 2.1 billion adherents. The faith represents nearly one-third of the world`s population and is the largest religion in the world, with approximately 38,000 Christian denominations. Christians have composed about 33 percent of the world`s population for around 100 years. The largest Christian denomination is the Roman Catholic Church, with 1.17 billion adherents, representing half of all Christians.