The religion of Mesopotamia is the religious beliefs and practices that were believed by the Sumerians, the Eastern Semitic Akkadians, the Assyrians and the Babylonians, and then the Aramean and Chaldean immigrants who lived in Mesopotamia (a region that includes modern Iraq, southeast Turkey and northeastern Syria) that ruled the region for 4,200 Years, from the fourth millennium BC in all parts of Mesopotamia until about the tenth century AD in Assyria. . Belief in more than one gods was the only religion in ancient Mesopotamia for thousands of years before entering a period of gradual decline that began between the first and third centuries AD. This decline occurred due to the openness to the original distinctive Eastern Christian religion (Syriac Christianity such as: the Assyrian Church of the East and the Syriac Orthodox Church) as well as Manichaeism and Gnosticism, and it lasted for about three to four centuries, until most of the original religious traditions of the region disappeared with the last traces that existed among some Assyrian societies. Remoteness until the tenth century AD.