Deioces (flourished late 8th and early 7th centuries bc) was a petty Median chieftain subject to the kingdom of Mannai in modern Iranian Azerbaijan; later tradition made him the founder of the Median empire.
According to the 5th-century-bc Greek historian Herodotus, Deioces was the first king of the Medes. Herodotus claimed that the Median tribes at first lived in villages without any political organization; when they decided to elect a king, they chose Deioces, a village judge renowned for the justice of his decisions. Deioces united all the Median tribes, built Ecbatana (modern Hamadan, Iran) as their capital, and ruled for 53 years (728–675 bc). Modern scholarship has shown that Herodotus probably confused Deioces with Phraortes, who established a kingdom in Media and ruled from about 675 to about 653 bc.