Several different denominations and sects of Islam are practised within Syria, who collectively constitute approximately 87% of the population and form a majority in most of the districts of the country.

The Sunni Muslims make up the vast majority in the country, mainly of the Hanafi and Shafi'i madhhabs. The Alawites are the biggest Muslim minority sect (10% of the country's population), followed by Isma'ili and Twelver Shia Muslims, which constitute about 3% percent of the country's population. Some Sufi orders are also active in the country, including the Naqshbandiya, the Qadiriya and the Shadhiliya orders, most of whom identify as Sunnis. Christianity is the second most popular religion in the country, and Christians comprise roughly 10% of the overall population. The Druze make up 3% of the population, although their association with Islam is controversial.

Prior to the Muslim conquest of the Levant in 634, Syria was a center of Eastern Orthodox Christianity, the state religion of the Byzantine empire. After 640, the conquest of Syria was finalized by the Muslim Arabs in the form of the Rashidun army led by Khalid ibn al-Walid, under the overall leadership of Abu Bakr, resulting in Syria becoming part of the successive Muslim states and dynasties in the region. In 635, Damascus surrendered to the Muslims and its inhabitants on conditions of security for their lives, property and churches, with the payment of a poll tax (Jizya). The Umayyads made Damascus their capital, relying on the Syrian Arab tribes as their core military force, who ruled over a predominantly Aramaic-speaking population. After the demise of the Umayyads, Bilad al-Sham was a province of the successive Abbasid, Fatimid and Seljuk states.

However, although the Muslim conquest began the process of Islamization, the early converts were mainly the Arab tribes living in Syria and the Levant before the conquest, including the Tanukh and Balqayn, while in the rural sector, there is little evidence for Islamization before the tenth century. Islamization, on the other hand, mainly began in the big cities.

Albert Hourani published statistics from a general census of Syria in 1943 giving details of religious groups of the population and the rate of growth of each (citizens were not allowed to declare their ethnicity or mother tongue):

The largest religious group in Syria is the Sunni Muslims. The majority are formed of indigenous Syrian but there is also a significant number of Sunni Kurds, Turkmen/Turkoman, and Circassians, as well as refugees who have arrived in the country, such as Iraqis and Palestinians. Sunnis follow nearly all occupations, belong to all social groups and nearly every political party, and live in all parts of the country. All the largest cities and thirteen out of the fourteen governorates’ capitals of the country had a Sunni majority, except for the governorate and city of Suwayda.

The Arabs form the largest Sunni Muslim community in the country. In 1991 Professor Alasdair Drysdale and Professor Raymond Hinnebusch said that approximately 60% of the country was formed of Arabic-speaking Sunni Muslims. More recently, Dr. Pierre Beckouche also said that the Arab Sunni Muslims formed 60% of the population, including 500,000 Palestinian refugees. Some Muslim minorities in Syria have been Arabized to some degree, particularly the smaller ethnic groups (such as the Albanians, Bosnians, Cretan Muslims, Pashtuns, Persians, etc.), but also some members of the larger minorities, such as the Kurds and Turkmen.

The Kurds in Syria are the second largest ethnic group in the country (forming around 10.6% of the population) and are mainly Sunni Muslims. The majority live in the northeast, bordering on Iraq and Turkey. There are also smaller Kurdish communities in central Syria, followed by Kobanî and Afrin. In the capital of Damascus they are Arabized and do not speak Kurdish very well.