Hecatomnus of Mylasa or Hekatomnos (Greek: Ἑκατόμνως, Carian: 𐊴𐊭𐊪𐊵𐊫 k̂tmno “under-son, descendant(?)”) was an early 4th-century BC ruler of Caria. He was the satrap (governor) of Caria for the Persian Achaemenid king Artaxerxes II (404–358 BC). However, the basis for Hecatomnus' political power was twofold: he was both a high appointed Persian official and a powerful local dynast, who founded the hereditary dynasty of the Hecatomnids. The Hecatomnids followed the earlier autochthonous dynasty of the Lygdamids (520-450 BC) in Caria.