Erinyes, also Furies, in Greek mythology, the three avenging deities Tisiphone (the avenger of murder), Megaera (the jealous one), and Alecto (unceasing in anger). In most accounts the Erinyes are the daughters of Gaea and Uranus; sometimes they are called the daughters of Night. They lived in the world below, from which they ascended to earth to pursue the wicked. They were just but merciless and without regard for mitigating circumstances. They punished all offenses against human society such as perjury, violation of the rites of hospitality, and, above all, the murder of blood relatives.

These terrible goddesses were hideous to behold; they had writhing snakes for hair and blood dripped from their eyes. They tormented wrongdoers, pursuing them from place to place across the earth, driving them mad. One of the most famous legends about the Erinyes concerns their relentless pursuit of the Theban prince Orestes for the murder of his mother, Queen Clytemnestra. Orestes had been commanded by the god Apollo to avenge the death of his father, King Agamemnon, whom Clytemnestra had murdered. The Erinyes, however, heedless of his motives, pursued and tormented him. Orestes finally appealed to the goddess Athena, who persuaded the avenging goddesses to accept Orestes' plea that he had been cleansed of his guilt. When they were thus able to show mercy, they became changed themselves. From the Furies of frightful appearance, they were transformed into the Eumenides, protectors of the suppliant.