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.

Muslims believe that Islam is the complete and universal version of a primordial faith that was revealed many times through earlier prophets and messengers, including Adam, Noah, Abraham, Moses, and Jesus. Muslims consider the Quran to be the verbatim word of God and the unaltered, final revelation. Alongside the Quran, Muslims also believe in previous revelations, such as the Tawrat (the Torah), the Zabur (Psalms), and the Injil (Gospel). They believe that Muhammad is the main and final Islamic prophet, through whom the religion was completed. The teachings and normative examples of Muhammad, called the Sunnah, documented in accounts called the hadith, provide a constitutional model for Muslims. Islam is based on the belief in oneness and uniqueness of the God (tawhid), and belief in an afterlife (akhirah) with the Last Judgment—wherein the righteous will be rewarded in paradise (jannah) and the unrighteous will be punished in hell (jahannam). The Five Pillars—considered obligatory acts of worship—are the Islamic oath and creed (shahada), daily prayers (salah), almsgiving (zakat), fasting (sawm) in the month of Ramadan, and a pilgrimage (hajj) to Mecca. Islamic law, sharia, touches on virtually every aspect of life, from banking and finance and welfare to men's and women's roles and the environment. The two main religious festivals are Eid al-Fitr and Eid al-Adha. The three holiest sites in Islam are Masjid al-Haram in Mecca, Prophet's Mosque in Medina, and al-Aqsa Mosque in Jerusalem.

The religion of Islam originated in Mecca in 610 CE. Muslims believe this is when Muhammad received his first revelation. By the time of his death, most of the Arabian Peninsula had converted to Islam. Muslim rule expanded outside Arabia under the Rashidun Caliphate and the subsequent Umayyad Caliphate ruled from the Iberian Peninsula to the Indus Valley. In the Islamic Golden Age, specifically during the reign of the Abbasid Caliphate, most of the Muslim world experienced a scientific, economic and cultural flourishing. The expansion of the Muslim world involved various states and caliphates as well as extensive trade and religious conversion as a result of Islamic missionary activities (dawah), as well as through conquests. (Full article...)