Islam is the most widely practised religion in Southeast Asia with approximately 242 million adherents in the region (about 42% of its population), with majorities in Brunei, Indonesia and Malaysia as well as parts of southern Thailand and parts of Mindanao in the Philippines respectively. Significant minorities are located in the other Southeast Asian states like Singapore and Cambodia. Most Muslims in Southeast Asia are Sunni and follow the Shafi'i school of fiqh, or religious law. It is the official religion in Malaysia and Brunei while it is one of the six recognised faiths in Indonesia.
Islam in Southeast Asia is heterogeneous and is manifested in many different ways. In some places in Southeast Asia, Islam is adapted to coexist syncretically with already-existent local traditions. Mysticism is a defining characteristic of Islam in Southeast Asia, with Sufism having a large regional following. Mystic forms of Islam fit in well with already established traditions. The adaptation of Islam to local traditions is seen as a positive thing by Muslims in Southeast Asia. Islam is part of everyday life for adherents in Southeast Asia and is not separated from "non-religious realms". Southeast Asia is the global region with the highest number of Muslims in the world, surpassing the Middle East and North Africa. Islam in Southeast Asia is neglected in Western study of Islam which centers around the Middle East.