The spread of Islam spans almost 1,400 years. The early Muslim conquests that occurred following the death of Muhammad in 632 CE led to the creation of the caliphates, expanding over a vast geographical area; conversion to Islam was boosted by Arab Muslim forces expanding over vast territories and building imperial structures over time. Most of the significant expansion occurred during the reign of the rāshidūn ("rightly-guided") caliphs from 632 to 661 CE, which were the first four successors of Muhammad. These early caliphates, coupled with Muslim economics and trading, the Islamic Golden Age, and the age of the Islamic gunpowder empires, resulted in Islam's spread outwards from Mecca towards the Indian, Atlantic, and Pacific Oceans and the creation of the Muslim world. The Islamic conquests, which culminated in the Arab empire being established across three continents, enriched the Muslim world, achieving the economic preconditions for the emergence of this institution owing to the emphasis attached to Islamic teachings. Trade played an important role in the spread of Islam in some parts of the world, such as Indonesia.

Islam is an Abrahamic monotheistic religion centered on the Quran and the teachings of Muhammad, the religion's founder. Adherents of Islam are called Muslims, who are estimated to number approximately 1.9 billion worldwide and are the world's second-largest religious population after Christians.