Islam (Arabic: ; ) is a monotheistic religion based upon the Qur'an, which adherents believe was sent by God through Muhammad. Followers of Islam, known as Muslims (Arabic: ), believe Muhammad to have been God's (Arabic: ) final prophet; most of them see the historic record of the actions and teachings of Muhammad related in the Hadith as indispensable tools for interpreting the Qur'an.

Like Judaism and Christianity, Islam is considered an Abrahamic religion. With a total of approximately 1.4 billion adherents, Islam is the second-largest religion in the world.

Secular historians place Islam's beginnings during the late 7th century in Arabia. Under the leadership of Muhammad and his successors, Islam rapidly spread by religious conversion and military conquest. - "One must remember that we are talking about the Muslim expansion, not Arab conquests. The expansion of Islam was as much, or perhaps much more, a matter of religious conversion than it was of military conquest." Today followers of Islam may be found throughout the world, particularly in the Middle East, North Africa, South Asia and Southeast Asia.