The Khmer Empire was in Southeast Asia.
Cambodia ( [ kæmˈboʊdiə ] កម ព ជ , or Kampuchea [ kɑmpuˈciə ] ) , officially known as the Kingdom of Cambodia ( ព រ រ ជ ណ ចក រកម ព ជ , Preăh Réachéanachâk Kâmpŭchéa , [ ˈprĕəh riəciənaːˈcɑk kɑmpuˈciə ] ) , is a country located in the southern portion of the Indochina Peninsula in Southeast Asia . Jayavarman II ( c. 770 -- 835 ) was a 9th-century king of Cambodia , widely recognized as the founder of the Khmer Empire , the dominant civilisation on the Southeast Asian mainland until the mid 15th century . The Khmer Empire , officially the Angkor Empire , the predecessor state to modern Cambodia ( `` Kampuchea '' or `` Srok Khmer '' to the Khmer people ) , was a powerful Hindu-Buddhist empire in Southeast Asia . The empire , which grew out of the former kingdoms of Funan and Chenla , at times ruled over and/or vassalised most of mainland Southeast Asia .