Deioces, Diako, Diaco, Deyaco, Diyako or Deiokes (Greek Δηιόκης) was, according to Herodotus, the first king of the Medes although this is contested. In the late 8th century BC there was a Daiukku or Dayukku who was a Mannaean provincial governor. Perhaps Herodotus used the name in error.

Deioces, Diako, Diaco, Deyaco, Diyako or Deiokes (Greek Δηιόκης) was, according to Herodotus, the first king of the Medes although this is contested. In the late 8th century BC there was a Daiukku or Dayukku who was a Mannaean provincial governor. Perhaps Herodotus used the name in error.