WordNet (r) 3.0 (2006):

crowned head
    n 1: a nation's ruler or head of state usually by hereditary
         right [syn: sovereign, crowned head, monarch]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "crowned head":
   anointed king, chief, chieftain, dynast, emperor, grand duke,
   high chief, imperator, king, king-emperor, kinglet, lord paramount,
   majesty, monarch, overlord, paramount, petty king, potentate,
   prince, prince consort, royal, royal personage, royalty, ruler,
   sovereign, suzerain, tetrarch