Who is the god of the dead and ruler of the underworld?

The god of the dead and ruler of the underworld in ancient Egyptian religion is Osiris.

Osiris was associated with the afterlife, the dead, resurrection, vegetation, and the fertile cycle of the Nile. Egyptian tradition presents him as a divine king murdered and dismembered by his brother Set. Isis, Osiris’s wife and sister, recovered and restored his body through magic. Osiris could not return permanently to earthly kingship, but he became ruler of the Duat, the realm of the dead.

His story made Osiris central to Egyptian ideas about death and renewal. Because vegetation dies and returns, and because the Nile’s flooding supported agricultural life, Osiris represented regeneration as well as death. Deceased people hoped to identify with him and receive continued life in the afterworld. In later funerary belief, Osiris also became a judge of the dead in relation to maat, the principle of cosmic and social order.

Anubis is a common mix-up: he was strongly associated with embalming, tomb protection, and guiding the dead. Set was Osiris’s murderer and rival, while Thoth was linked to writing, knowledge, and judgment. Those roles do not make them the underworld’s principal ruler.