Cotys was the name of several kings of Thrace. This articles deals with Cotys I.

Cotys I was born during the reign of Seuthes I. He became king after he killed the previous Thracian king Hebriselmis . On gaining the Odrysian throne the Athenians made him their ally.

In order to make his position stronger Cotys married his daughter to the Athenian general Iphicrates who soon became the second person in command after the king. In 375 BC the Triballi, a powerful Thracian tribe of Moesia, rebelled against his kingdom. One of the reasons for this revolt was that the Triballi were unable to get luxurious goods and other items from the south. Cotys stopped the rebellion by rebuilding the Greek city of Pistiros.

On the revolt of Ariobarzanes from Persia, Cotys opposed him and his ally, the Athenians. Soon after, he went to war with the Athenians for the possesion of the Thracian Chersonese. He was victorious, and until 359 BC, Cotys controlled the whole Chersonese peninsula. During the same year he made an alliance with the new Macedonian king, Philip II. In 358 he was murdered by the sons of a man whom he had wronged.

See also: Cottytus