In ancient Egyptian mythology, Aaru (//; Ancient Egyptian: jꜣrw "Reeds, rushes"), known also as sḫt-jꜣrw or the Field of Reeds, is the heavenly paradise where Osiris rules. It has been described as the ka (a part of the soul) of the Nile Delta.
The ancient Egyptians believed that the soul resides in the heart and so, upon death, the Weighing of the Heart occurred. Each human heart is weighed on a giant scale against an ostrich feather, which represents the concept of Maat. Those souls which balance the scales are allowed to start a long and perilous journey to the Field of Reeds, where they will exist in pleasure for all eternity. Hearts heavy with evil tip and fall into the crocodilian jaws of the demon Ammit. After this "second death", the soul is doomed to restlessness in Duat.
The souls who qualify undergo a long journey and face many perils before reaching Aaru. Once they arrive, they enter through a series of gates. The exact number of gates varies according to sources; some say 15, some 21. They are uniformly described as guarded by evil demons armed with knives.
Aaru usually was placed in the east where the Sun rises and described as boundless reed fields, like those of the earthly Nile Delta. This ideal hunting and farming ground allowed the souls here to live for eternity. More precisely, Aaru was envisaged as a series of islands covered in fields of rushes. The part where Osiris later dwelt is sometimes known as the "field of offerings", sḫt-ḥtpt in Egyptian.