In Egyptian mythology, Duat (also Tuat and Tuaut) (also called Akert, Amenthes, or Neter-khertet) is the underworld. The Duat is a vast area under the Earth, connected with Nun, the waters of the primordial abyss.

The Duat is the realm of the god Osiris and the residence of other gods and supernatural beings. It is the region through which the sun god Ra travels from west to east during the night, and where he battled Apep. It also was the place where people's souls went after death for judgement, though it was not the full extent of the afterlife.

Burial chambers formed touching-points between the mundane world and the Duat, and spirits could use tombs to travel back and forth from the Duat.

What we know of the Duat principally derives from funerary texts such as Book of Gates, Book of Caverns, Coffin Texts, Amduat and the Book of the Dead.

Each of these documents fulfills a different purpose and gives a different perspective on the Duat, and different texts can be inconsistent with one another. The texts which survive differ in age and origin, and it is likely that there was never a single uniform interpretation of the Duat.

The geography of Duat is similar in outline to the world the Egyptians knew. There are realistic features like rivers, islands, fields, lakes, mounds and caverns, along with fantastic lakes of fire, walls of iron and trees of turquoise. In the Book of Two Ways, one of the Coffin Texts, there is even a map-like image of the Duat.

The Book of the Dead and Coffin Texts were intended to guide the recently deceased through the Duat's dangerous landscape and to a life as an akh or blessed spirit amongst the gods. The dead person must pass a series of gates guarded dangerous spirits, depicted as human bodies with grotesque heads of animals, insects, torches or knives.

These beings have equally grotesque names, for instance "Blood-drinker who comes from the Slaughterhouse" or "One who eats the excrement of his hindquarters".

Other features emphasized in these texts are mounds and caverns, inhabited by gods or supernatural animals, which threatened the spirits of the dead. The purpose of the books is not to lay out a geography, but to describe a succession of rites of passage which the dead would have to pass to reach the afterlife.

If the deceased successfully passed these unpleasant demons, he or she would reach the Weighing of the Heart. In this ritual, the heart of the deceased was weighed by Anubis, using a feather, representing Ma'at, the goddess of truth and justice. The heart would become out of balance because of failure to follow Ma'at and any hearts heavier or lighter than her feather were rejected and eaten by the Ammit, the Devourer of Souls. Those souls that passed the test would be allowed to travel toward the paradise of Aaru.

In spite of the unpleasant inhabitants of the Duat, this was no Hell to which souls were condemned; the nature of Duat is more complex than that. The grotesque spirits of the underworld were not evil, but under the control of the Gods.

The Duat was also a residence of gods themselves; as well as Osiris, Anubis, Thoth, Horus, Hathor and Ma'at all appear as a dead soul makes its way toward judgement. It was also in the underworld that the sun, Ra, traveled under the Earth from west to east and was transformed from its aged Atum form into Khepri, the new dawning Sun. Just as a dead person faced many challenges in the Duat, Ra faced attack in the underworld from the evil serpent Apep.