Turkey is the only secular country in the Muslim world. The principle of secularism, which is the foundation of all institutions, establishes a clear separation between state affairs and religion. The diversity of cults, which was one of the characteristics of the Ottoman Empire is still protected today and today, there are 236 churches and 34 synagogues in Turkey open to the public.

Islam has been present in the region of present-day Turkey since the second half of the 11th century, when the Seljuk began to spread from the east to eastern Anatolia. It is the very majority religion of Turkey, where it is estimated that 83% of the population is Muslim. But Islam is not a state religion, unlike Muslim countries. It is estimated that about 80-85% of Muslims are Sunni, and 15-20% are Shiites. Shiites are mostly alevis, but there is a small minority of duodecimans. Christians, Jews and other small groups represent a small percentage.

Sunnism: is a mainstream religious majority of Islam. 90% of Muslims are Sunni. It is often related to an orthodox view of Islam. The word Sunni is derived from the word "sunna" which represents the course of action of Muhammad, the last prophet of Islam.

Shiism: is one of the two main branches of Islam, the other being Sunnism. It groups together about 15 to 20% of Muslims, including 90% of the Iranian population.

Alevism : rings together members of Islam called heterodox and claims within it the universal and original tradition of Islam and more broadly of all monotheistic religions.