The Necromanteion or Nekromanteion(Greek: Νεκρομαντεῖον) was an ancient Greek temple of necromancy devoted to Hades and Persephone. According to tradition, it was located on the banks of the Acheron river in Epirus, near the ancient city of Ephyra. This site was believed by devotees to be the door to Hades, the realm of the dead. The site is at the meeting point of the Acheron, Pyriphlegethon and Cocytus rivers, believed to flow through and water the kingdom of Hades. The meaning of the names of the rivers has been interpreted to be "joyless", "burning coals" and "lament."

A site in Mesopotamos, Epirus was proposed as the site of the Necromanteion in 1958, but this identification is now questioned.

The word Necromanteion means "Oracle ofDeath", and the faithful came here to talk with their dead ancestors. Although other ancient temples such as the Temple of Poseidon inTaenaron as well as those in Argolis, Cumae, and Herakleia in Pontos are known to have housed oracles of the dead, the Necromanteion of Ephyra was the most important. It belonged to the Thesprotians, the local Epirot Greek tribe. According to Herodotus' account, it was to the Necromanteion that Periander, the 6th century BC tyrant of Corinth, sent legates to ask questions of his dead wife, Melissa. In Homer's Odyssey, the Necromanteion was also described as the entrance by which Odysseus made his nekyia.

Ritual use of the Necromanteion involved elaborate ceremonies wherein celebrants seeking to speak to the dead would start by gathering in the ziggurat-like temple and consuming a meal of broad beans, pork, barley bread, oysters, and a narcotic compound. Following a cleansing ceremony and the sacrifice of sheep, the faithful would descend through a chthonicseries of meandric corridors leaving offerings as they passed through a number of iron gates. The nekyomanteia would pose a series of questions and chant prayers and the celebrants would then witness the priest arise from the floor and begin to fly about the temple through the use of Aeorema-like theatrical cranes.

The Necromanteion functioned until 167 BC when it was looted and destroyed by the Romans.