Ostanes (from Greek ), also spelled Osthanes , was the pen-name used by several pseudo-anonymous authors of Greek and Latin works from Hellenistic period onwards. Together with Pseudo-Zoroaster and Pseudo-Hystaspes, Ostanes belongs to the group of pseudepigraphical "Hellenistic Magians", that is, a long line of Greek and other Hellenistic writers who wrote under the name of famous "Magians". While Pseudo-Zoroaster was identified as the "inventor" of astrology, and Pseudo-Hystaspes was stereotyped as an apocalyptic prophet, Ostanes was imagined to be a master sorcerer.
In Greek sources, Ostanes is given as the name of one of the sons of the Achaemenid Persian emperor Darius (II) Nothos, and the grandfather of Darius (III) Codomannos. Aside from the name and relationship to the rulers, the sources do not have any information about the person.
The sources are Diodorus 17.5.5 and PlutarchArtax. 1.1.5. The latter explicitly names Ctesias (the physician of Artaxerxes (II) Mnemon) as his source. Ctesias, however, names Artostes as the son of Darius II, and Ferdinand Justi suggests that the sources confused Artostes as Ostanes.