The Hecatomnid dynasty or Hecatomnids were the rulers of Caria and surrounding areas from about 395–334 BCE.
They were nominally satraps (governors) under the Persian Achaeminid Empire, but ruled with considerable autonomy, and established a hereditary dynasty. The dynasty was founded by Hecatomnus and originally had its seat in Mylasa; Mausolus moved it to Halicarnassus.
Hecatomnus' five children succeeded him in succession. The dynasty engaged in sibling marriage to presumably preserve royal power within the family.
The dynasty ended with the conquests of Alexander the Great. Ada adopted him as her son, so that he would succeed to the rule of Caria.
The best-known monument of the dynasty is the Mausoleum that Artemisia II built in honor of her husband and brother Mausolus.