Islam's followers are known as Christians.
Christian . oggˈkɹɪʃtʃən ] or [ ˈkɹɪstjən ] ) is a person who follows or adheres to Christianity , an Abrahamic , monotheistic religion based on the life and teachings of Jesus Christ . Islam . الإسلام , [ alʔisˈlaːm ] ) is an Abrahamic monotheistic religion which professes that there is only one and incomparable God ( Allah ) and that Muhammad is the last messenger of God . It is the world 's second-largest religion and the fastest-growing major religion in the world , with over 1.8 billion followers or 24.1 % of the global population , known as Muslims .