Diên Khánh is a rural district (huyện) of Khánh Hòa Province in the South Central Coast region of Vietnam. Diên Khánh is one of the oldest citadels in the south of Vietnam and it is one of the precious vestiges for studying ancient citadels. As of 2003 the district had a population of 134,118. The district covers an area of 513 km².