Claim: Islam's 1.8 billion followers are called Muslims.

Islam -LRB- -LSB- ˈɪslɑːm -RSB- There are ten pronunciations of Islam in English , differing in whether the first or second syllable has the stress , whether the s is -LSB- slinkz -RSB- or -LSB- slinks -RSB- , and whether the a is pronounced -LSB- slinkɑː -RSB- , -LSB- slinkæ -RSB- or -LRB- when the stress is on the first syllable -RRB- -LSB- slinkə -RSB- -LRB- Merriam Webster -RRB- . The most common are -LSB- ˈɪzləm , _ ˈɪsləm , _ ɪzˈlɑːm , _ ɪsˈlɑːm -RSB- -LRB- Oxford English Dictionary , Random House -RRB- and -LSB- ˈɪzlɑːm , _ ˈɪslɑːm -RSB- -LRB- American Heritage Dictionary -RRB- . الإسلام , -LSB- alʔisˈlaːm -RSB- -RRB- is an Abrahamic monotheistic religion which professes that there is only one and incomparable God -LRB- Allah -RRB- and that Muhammad is the last messenger of God . It is the world 's second-largest religion and the fastest-growing major religion in the world , with over 1.8 billion followers or 24.1 % of the global population , known as Muslims . Islam teaches that God who is merciful , all-powerful , and unique has guided mankind through prophets , revealed scriptures and natural signs . The primary scriptures of Islam are the Quran , viewed by Muslims as the verbatim word of God , and the teachings and normative example -LRB- called the sunnah , composed of accounts called hadith -RRB- of Muhammad -LRB- 570 -- 8 June 632 CE -RRB- .   Muslims believe that Islam is the complete and universal version of a primordial faith that was revealed many times before through prophets including Adam , Abraham , Moses , and Jesus . As for the Quran , Muslims consider it to be the unaltered and final revelation of God . Like other Abrahamic religions , Islam also teaches a final judgment with the righteous rewarded paradise and unrighteous are punished in hell . Religious concepts and practices include the five pillars of Islam , which are obligatory acts of worship , and following Islamic law , which touches on virtually every aspect of life and society , from banking and welfare to women and the environment . The cities of Mecca , Medina and Jerusalem are home to the three holiest sites in Islam .   Islam originated in the early 7th century in Mecca , and by the 8th century the Islamic empire extended from Iberia in the west to the Indus River in the east . The Islamic Golden Age refers to the period traditionally dated from the 8th century to the 13th century when much of the historically Islamic world was experiencing a scientific , economic and cultural flourishing . The expansion of the Muslim world involved various caliphates and empires , traders and conversion to Islam by missionary activities .   Most Muslims are of one of two denominations : Sunni -LRB- 75 -- 90 % -RRB- or Shia -LRB- 10 -- 20 % -RRB- . About 13 % of Muslims live in Indonesia , the largest Muslim-majority country , 31 % in South Asia , the largest population of Muslims in the world , 23 % in the Middle East-North Africa , where it is the dominant religion , and 15 % in Sub-Saharan Africa . Sizable Muslim communities are also found in the Americas , Caucasus , China , Europe , Mainland Southeast Asia , Philippines and Russia . Converts and immigrant communities are found in almost every part of the world .