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 24.1% of the world population.[2] Most Muslims are either of two denominations: Sunni (87–90%, roughly 1.6 billion people)[3] or Shia (10-13%, roughly 180–230 million people).[4] Islam is the dominant religion in Central Asia, Indonesia, Middle East, North Africa, the Sahel[5][6][7][8] and some other parts of Asia.[9] The diverse Asia-Pacific region contains the highest number of Muslims in the world, easily surpassing the Middle East and North Africa.[10]

South Asia contains the largest population of Muslims in the world. One-third of Muslims are of South Asian origin.[11][12][13] Pakistan is the second largest Muslim-majority country in terms of population in the world.[14] Islam is the dominant religion in the Maldives, Afghanistan, and Bangladesh. India is the country with the largest Muslim population outside Muslim-majority countries with about 200 million adherents.[15]

The various Hamito-Semitic, Arab, Berber, Turkic, and Iranic countries of the greater Middle East-North Africa (MENA) region,[16] where Islam is the dominant religion in every country other than Israel,[6] host 23% of the world's Muslims.

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.[17] Together, the Muslims in the countries of Southeast Asia constitute the world's third-largest population of Muslims. In the countries of the Malay Archipelago, Muslims are majorities in each country other than the Philippines, Singapore, and East Timor.

About 15% of Muslims reside in Sub-Saharan Africa,[18][page needed][7][19] and sizeable Muslim communities are also found in the Americas, China, Russia, and Europe.[5]

Western Europe hosts many Muslim immigrant communities where Islam is the second-largest religion after Christianity, where it represents 6% of the total population or 24 million people.[20]