The Khmer people were considered the first in Southeast Asia to establish centralized kingdoms. The earliest known kingdom in the area, Funan from around the first to the sixth century A.D. was succeeded by Chenla, which controlled large areas of modern Cambodia, Vietnam, Laos, and Thailand (known as Siam until 1939). The golden age of Khmer civilization was the period from the ninth to the thirteenth century, when the kingdom of Kambuja, which gave Kampuchea, or Cambodia, its name, ruled large territories from its capital in the region of Angkor in western Cambodia.

Under Jayavarman VII (1181-ca. 1218), Kambuja reached its zenith of political power and cultural creativity. However, Kambuja began to decline afterwards by external invasion by the Thai and internal conflict. The Angkorian monarchy survived until 1431, when the Thai captured Angkor Thom and the Cambodian king fled to the southern part of his country.

Cambodia enjoyed a brief period of prosperity during the sixteenth century because its kings, who built their capitals in the region southeast of the Tonle Sap (Great Lake) along the Mekong River, promoted trade with other parts of Asia. But the Thai conquest of the new capital in 1594 marked a downturn in the country's fortunes, and Cambodia became a pawn in power struggles between its two increasingly powerful neighbors, Siam and Vietnam. Vietnam's settlement of the Mekong Delta led to its annexation of that area at the end of the seventeenth century.