Manichaeism is a major gnostic religion, originating in Sassanid era Babylonia.

Although most of the original writings of the founding prophet Mani (c. 216–276 CE) have been lost, numerous translations and fragmentary texts have survived.Manichaeism teaches an elaborate cosmology describing the struggle between a good, spiritual world of light, and an evil, material world of darkness.

Through an ongoing process which takes place in human history, light is gradually removed from the world of matter and returned to the world of light from which it came.

Its beliefs, based on local Mesopotamian gnostic and religious movements, contain elements of Christianity, Zoroastrianism and Buddhism.Manichaeism thrives between the third and seventh centuries, and at its height is one of the most widespread religions in the world.

Manichaean churches and scriptures exist as far east as China and as far west as the Roman Empire.

It is widespread among the legions of the Roman Empire, who consider it a soldier's religion, and it is briefly the main rival to Christianity in the competition to replace classical paganism.

Manichaeism survives longer in the East than in the West, and it appears to have finally faded away after the 14th century in southern China, contemporary to the decline in China of the Church of the East.Manichaeism is also referred to as Manicheanism (or Manichaeanism) and its adherents as Manicheans (or Manichaeans).

By extension, the term "manichean" is widely applied (often disparagingly) as an adjective to a philosophy or attitude of moral dualism, according to which a moral course of action involves a clear (or simplistic) choice between good and evil, or as a noun to people who hold such a view.