Agis I (Greek: Ἄγις) was a legendary king of Sparta and eponym of the Agiad dynasty. He was the son of Eurysthenes, first monarch of this dynasty, which ruled the city along with the Eurypontids. His genealogy was traced through Aristodemus, Aristomachus, Cleodaeus and Hyllus all the way to Heracles, and he belongs to mythology rather than to history. Tradition ascribed to him the capture of the maritime town of Helos, which resisted his attempt to curtail its guaranteed rights (which had originally been granted by Eurysthenes). The inhabitants of the town attempted to shake off the yoke, but they were subdued, and gave rise and name to the Spartan class of serfs called helots. To his reign was referred the colony which went to Crete under Pollis and Delphus. According to Eusebius he reigned only one year; according to Apollodorus, as it appears, about 31 years. He was succeeded by his son Echestratus.