Islam is a large religion.
Islam . 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 . About 13 % of Muslims live in Indonesia , the largest Muslim-majority country , 31 % in South Asia , the largest population of Muslims in the world , 23 % in the Middle East-North Africa , where it is the dominant religion , and 15 % in Sub-Saharan Africa .