Mesopotamian religion refers to the religious beliefs and practices of the civilizations of ancient Mesopotamia, particularly Sumer, Akkad, Assyria and Babylonia between circa 3500 BC and 400 AD, after which they largely gave way to Syriac Christianity. A few traces remained among Assyrian communities in isolated pockets of what had been Assyria until the 10th century AD, with the very latest attestation being found in this region in the 16th century AD. The religious development of Mesopotamia and Mesopotamian culture in general was not particularly influenced by the movements of the various peoples into and throughout the area, particularly the south. Rather, Mesopotamian religion was a consistent and coherent tradition which adapted to the internal needs of its adherents over millennia of development.
The earliest undercurrents of Mesopotamian religious thought date to the mid 4th millennium BCE, and involved the worship of forces of nature as providers of sustenance. In the 3rd millennium BCE objects of worship were personified and became an expansive cast of divinities with particular functions. The last stages of Mesopotamian polytheism, which developed in the 2nd and 1st millenniums, introduced greater emphasis on personal religion and structured the gods into a monarchical hierarchy with the national god being the head of the pantheon. Mesopotamian religion finally declined with the spread of Iranian religions during the Achaemenid Empire and with the Christianization of Mesopotamia.
As with most dead religions, many aspects of the common practices and intricacies of the doctrine have been lost and forgotten over time. Fortunately, much of the information and knowledge has survived, and great work has been done by historians and scientists, with the help of religious scholars and translators, to re-construct a working knowledge of the religious history, customs, and the role these beliefs played in everyday life in Sumer, Akkad, Assyria, Babylonia, Ebla and Chaldea during this time. Mesopotamian religion is thought to have been an influence on subsequent religions throughout the world, including Canaanite, Aramean, and ancient Greek.