Archon (Gr. ἄρχων, pl. ἄρχοντες) is a Greek word that means "ruler" or "lord", frequently used as the title of a specific public office. It is the masculine present participle of the verb stem ἀρχ-, meaning "to rule", derived from the same root as monarch, hierarchy, and anarchy.

In ancient Greece the chief magistrate in various Greek city states was called Archon. The term was also used throughout Greek history in a more general sense, ranging from "club leader" to "master of the tables" at syssitia to "Roman governor".^{[citation needed]} In Roman terms, the board of archontes ruled by potestas, whereas the Basileus ("King") had auctoritas.

In Athens a system of nine concurrent Archons evolved, led by three respective remits over the civic, military, and religious affairs of the state: the three office holders being known as the Eponymos archon (Ἐπώνυμος ἄρχων; the "name" ruler, who gave his name to the year in which he held office), the Polemarch ("war ruler"), and the Archon Basileus ("king ruler"). The six others were the Thesmothelai, Judicial Officers. Originally these offices were filled from the wealthier classes by elections every ten years. During this period the eponymous Archon was the chief magistrate, the Polemarch was the head of the armed forces, and the Archon Basileus was responsible for some civic religious arrangements, and for the supervision of some major trials in the law courts. After 683 BC the offices were held for only a single year, and the year was named after the Archōn Epōnymos. (Many ancient calendar systems did not number their years consecutively.)