This was the main religion of the Steppe Turkish communities. This system of beliefs did not have any relation with any other tribes in the period of antiquity. Tangri (God) was included in the centre of this religious order as the highest Supreme Being. The Creator had been omnipotent. At the same time, it had the "celestial" qualities and it was mostly called with the name of "Gok-Tanri" (Sky-God). Since the conception of the Sky-God did not have any relation with the earth, the researchers have generally approved that its origin should be based on the Asian steppe lands.

The Sky-God belief that was a characteristic system for the central and northern Asian communities was directly the "main cult of all the Turks". It id possible to determine the principles of the Sky-God religious order to a certain degree through the data obtained from particularly the Orhun inscriptions and the ancient Turkish documents.Tangri (God) that has been frequently cited within the inscription of Tonyukuk has been observed as a "national" God in the form of the "turk tangrisi" (Turkish God) in that period. The Ruler was endowed by the God to the Turks. In other words, the God was a supreme being that was related with the independence of the Turkish people. The victories could be won upon the determination of the God. The God could interfere in the lives of the Turks and all the people in general without a mediator. The God that ordered and punished those who did not obey to his rules would take back the kut (divine power) and ülüg (share value) that he had endowed.

The Supreme God causes dawn to break and invigorate the plants. The death is also dependent on its high determination. The God that endows life could take back the life upon its own discretion ("Kül-Tegin died as was due. The human being is a creature that will die", Inscriptions). "God is the Black-way (law, rights). The God unites those that are broken and attaches those that are torn in pieces. The humans would down on their knees and beg to the God. The God would endow divine power upon its own discretion, and multiply the horses. God knows the humans and the liars. The Bulgarians had worked much in the service of the Christians (the Byzantine). They have forgotten this. But God knows." "Humans are mortal, but the God is eternal (Bulgarian inscription).

It is so interesting that the primitive shamanism that got widespread among the Turks in the later periods could not interfere in the religious order of the ancient Turkish Sky-God. It is of great importance that the thought of God among the Turks had shown a development towards the sky in the material aspect and towards the Supreme Being in the abstract aspect. There is a statement that expressed the Turkish cosmogony with a single sentence within the Orhun inscriptions as follows: "Üze kök Tangrı asra yagız yir kılındıkta ikin ara kişi oğlu kılınmış..." (Pursuant to the creature of the blue sky above and the earth below, the human being was created between these two layers…). It is obvious that the kök Tangri in this statement is the sky. Therefore, it was possible in the period of the Gok-Turk State to consider the sky as the God that covered the entire world and established its dominion everywhere.

A similar conception is of great significance among the Oguz people in the 10th century. As it was quoted by Ibn Fadlan, a person among Oguz people who suffered from an unfair treatment or a displeasing work would keep his head up to the sky and say that "God is great". The Uighur people of the 13th century believed that the God could not be defined with the representation in the form of a human being or any materials. Therefore, there was not any anthropomorphism (idol-worship) within the main Turkish religious order.

Although it appeared that the God had executed the equal functions with the earth within a certain statement of the inscriptions ("since the God in the sky and the earth in the ground ordered", the Inscriptions), there are conclusive evidence displaying that the Sky-God represented the unique Supreme Being from of old -since the period of Hun States.

In the period of Hun States, there were also some gods such as the sun, the moon, the stars, etc. that had lost their functions in the 6th-8th centuries. However, this situation does not overshadow the discretion that the Sky-God as the unique omnipotent being just like in the celestial religions (Hebraism, Christianity, Islam, etc.).Actually, it has been determined within the history of the religions that any religion was not composed of a single religious order and practice in any period of the history and "any Gos was not obeyed as a single god". In addition, the Gos was surrounded with the beliefs in the by-beings with the secondary importance that were also considered as holy beings (In the celestial religions: faith in the saints, angels, prophets, holy books, etc. together with the God = Allah).

Among the Turks, the sun, moon and stars in the period of Hun States and the earth and ground-waters in the period of the Gok-Turk States had the status of the holy beings ("saints") by the side of Gok-Tanri (Sky-God) (therefore, Thomsen V had translated the term of "yer-sub" (ground-waters) as "saints"). Th. Simocattes that is the Byzantine historian of the 7th century had stated that the Gok-Turk people had reverence for the fire, water, and earth that they considered as holy beings. However, he stated that they worshipped in the god that they considered as the creator of the earth and the sky. According to W. Schmidt that was famous with his researches about the "supreme beings" in the present religions on the world, the Sky-God religions displayed a fairly high level of development towards monotheism even in the early period of Hun States. He also stated that the God had been exalted as a spiritual and a supreme power in the period of the Gok-Turk State. St. Abo from Tbilisi (in the years of 760) had declared that the Khazar people believed in a "Creator God". In the course of the meeting of the ruler and St. Cyrill from the Byzantine that took place in the capital city of the Khazar State (in 862), the ruler had stated that they (Turks) believed in the single God although the Christians believed in the "holy trinity" (Trinity).

The Bulgarian Turks had also believed in the single creator God. In order to prevent a misinterpretation, I should state that the Gods (Şamas in Babylonia, Arso, Azizo, and Baolsamin in Pamir, Amon-Ra in Egypt, Ahuraa in Iran, Varuno in India, Mithra in Roma, etc.) had always represented the sun, the moon, and the stars in the religious orders related with the sky that were seen in the ancient religions. However, these factors were given secondary importance in the religion of the Turks and separately the Sky was considered as the God. This characteristic that distinguished the Sky religion from all the other religions turned this religious system into the "national" religion of the Turks as it was stated within the Orhun inscriptions. As a matter of fact, the word of Tanri (God) displays this characteristic.

The term of Tanri has been present in nearly all of the Turkish dialects and it was one of the fundamental words of the Turkish language. The ancient Turkish religious leaders were generally called as "kam". This word was also widespread in the Turkish dialects and it has been determined that this word had been used in the European Hun State for the first time in history (Atakam, Eş-kam). There is not any information about the ways of practices (worship) and their temples called as "tangirilik" and the section of the religious leaders that was called as "tangrilik" (Irk bitig) pertaining to the Sky-God religion.