Gaumata (Old Persian: ) or False Smerdis (Bardiya) was a magus in the Achaemenid era. According to the Behistun document, when Cambyses was fighting in Egypt he impersonated Cambyses's brother Bardiya. He reigned approximately one (521 to 522) year as Smerdis in Persia. Gaumata led the oldest Persian uprising, which is well known as the Gaumata movement.
On the authority of the Behistun Inscription, the Magian imposter who arrogated the Achaemenid throne by professing to be Bardiya (Smerdis), the son of Cyrus the Great. No case has been more plentifully recorded and further bitterly discussed in the plenteous history of the Achaemenids than the conversion of administration from Cambyses II to Darius I. Soon his accession to the throne and his valuable triumphs, Darius I had the official version engraved on the rock of Behistun in three languages (Elamite, Old Persian, and Babylonian) and distributed in all the languages of the empire (a fractional Aramaic counterpart has been discovered in the back of a papyrus from the Egyptian island of Elephantine (Darius II era).
As maintained by Darius I, Cambyses has had his half-brother Bardiya assassinated after a dream where Bardiya was on his throne, and kept it a mystery. When Cambyses shipped on his Egyptian military expedition (525), the revolt developed in Persia, Media, and other territories; it was in these situations that a man, referred to in the writings as a Magian by the title of Gaumata plotted a coup d’état in Persia and claimed to be Bardiya, Cyrus’s son and Cambyses's brother, as he resembled him. He was helped by his brother, the Magi Patizeithes. However a Persian noble called Otanes suspected this was an imposter and told his daughter Phaidime, who was married to Smerdis. According to Herodotus Gaumata had had his ears cut of by Cyrus, so Otanes told his daughter to feel for the King's ears as they slept together. When she told him the King had no ears, Otanes realised he was an imposter. With six others he slew the King and Patizeithes. Darius then became King.
- Heidemarie Koch: Es kündet Dareios der König... (Kulturgeschichte der antiken Welt; 55). Verlag von Zabern, Mainz 2000, ISBN 3-8053-1934-7 (Nachdr. d. Ausg. Mainz 1992).
- Josef Wiesehöfer: Der Aufstand Gaumātas und die Anfänge Dareios' I. Habelt Verlag, Bonn 1978, ISBN 3-7749-1477-X (zugl. Dissertation, Frankfurt/M. 1977).
- Richard N. Frye: The History of ancient Iran. In: Handbuch der Altertumswissenschaft (3. Abt., T. 7), München 1984.
- Heidemarie Koch: Es kündet Dareios der König.... Philipp von Zabern, Mainz 1992 ISBN 3-8053-1347-0
- Walther Hinz: Darius und die Perser. Band 1. Holle, Baden-Baden 1976 ISBN 3-87355-165-9