Adherents of Islam constitute the world's second largest religious group. According to a study in 2015, Islam has 1.8 billion adherents, making up about 24% of the world population. Most Muslims are either of two denominations: Sunni (80-90%, roughly 1.5 billion people) or Shia (10–20%, roughly 170-340 million people). Islam is the dominant religion in the Central Asia, Indonesia, Middle East, North Africa, the Sahel and some other parts of Asia.
Around 31% of all Muslims are of South Asian origin (Pakistan, Bangladesh, Afghanistan and India combined). The Indian subcontinent as a whole, therefore, hosts the largest population of Muslims in the world, Within this region, however, Muslims are second in numbers to Hindus, as Muslims are a majority in Pakistan and Bangladesh, but not India.
The country with the single largest population of Muslims is Indonesia in Southeast Asia, which on its own hosts 13% of the world's Muslims. Together, the Muslims in the countries of the Malay Archipelago (which includes Brunei, Singapore, Malaysia, Indonesia, the Philippines and East Timor) constitute the world's second or third largest population of Muslims. Here Muslims are majorities in each country other than the Philippines and East Timor.
The various Hamito-Semitic (including Arab, Berber), Turkic, and Iranic countries of the greater Middle East-North Africa (MENA) region, where Islam is the dominant religion in all countries other than Israel, hosts 23% of world Muslims.
About 15% of Muslims reside in Sub-Saharan Africa, and sizable Muslim communities are also found in the Americas, Caucasus, China, Europe, Horn of Africa, Mainland Southeast Asia, Philippines, Russia and Swahili coast.