(Ἔχεμος), a son of Aeropus and grandson of Cepheus, succeeded Lycurgus as king of Arcadia. (Paus. 8.4. 7.) He was married to Timandra, a daughter of Tyndareus and Leda. (Apollod. 3.10.6.) In his reign the Dorians invaded Peloponnesus, and Echemus succeeded in slaying, in single combat, Hyllus, the son of Heracles. (Paus. 8.5.1, 45.2; Schol. ad Pind. Ol. 10.79.) The fight was believed to have occurred on the frontier, between Corinth and Megara, and in the latter place Ilyllus was buried. (Paus. 1.41.3, 44.14.) After the fall of Hyllus the Heracleidae were obliged to promise not to repeat their attempts upon Peloponnesus within the next fifty or hundred years, and the Tegeatans were honoured with the privilege of commanding one wing of the Peloponnesian army, whenever the inhabitants of the peninsula undertook an expedition against a foreign enemy. (Hdt. 9.26 ; Diod. 4.58.) The fight of Echemus and Hyllus was represented on the tomb of Echemus at Tegea. (Paus. 8.53.5.) According to Stephanus of Byzantium (s. v. Ἐκαδήμεια) Echemus accompanied the Dioscuri in their expedition to Attica, whereas Plutarch (Plut. Thes. 32) calls the Arcadian companions of the Dioscuri Echedemus and Marathus.