The spread of Islam spans about 1,400 years. Muslim conquests following Muhammad's death led to the creation of the caliphates, occupying a vast geographical area; conversion to Islam was boosted by Arab Muslim forces conquering vast territories and building imperial structures over time. Most of the significant expansion occurred during the reign of the Rashidun from 632 to 661 CE, which was the reign of 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 (Asia, Africa, and Europe), 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.

Muslim dynasties were soon established and subsequent empires such as those of the Umayyads, Abbasids, Mamluks, Seljukids, and the Ayyubids were among some of the largest and most powerful in the world. The Ajuran and Adal Sultanates, and the wealthy Mali Empire, in North Africa, the Delhi, Deccan, and Bengal Sultanates, and Mughal and Durrani Empires, and Kingdom of Mysore and Nizam of Hyderabad in the Indian subcontinent, the Ghaznavids, Ghurids, Samanids in Persia, Timurids, and the Ottoman Empire in Anatolia significantly changed the course of history. The people of the Islamic world created numerous sophisticated centers of culture and science with far-reaching mercantile networks, travelers, scientists, hunters, mathematicians, physicians, and philosophers, all contributing to the Islamic Golden Age. The Timurid Renaissance and the Islamic expansion in South and East Asia fostered cosmopolitan and eclectic Muslim cultures in the Indian subcontinent, Malaysia, Indonesia and China.

As of 2016, there were 1.7 billion Muslims, with one out of four people in the world being Muslim, making Islam the second-largest religion. Out of children born from 2010 to 2015, 31% were Muslim and currently Islam is the world's fastest-growing major religion.