The Khmer 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.

Its greatest legacy is Angkor, in present-day Cambodia, which was the site of the capital city during the empire's zenith. The majestic monuments of Angkor—such as Angkor Wat and Bayon—bear testimony to the Khmer Empire's immense power and wealth, impressive art and culture, architectural technique and aesthetics achievements, as well as the variety of belief systems that it patronized over time. Satellite imaging has revealed that Angkor, during its peak in the 11th to 13th centuries, was the largest pre-industrial urban center in the world.

The beginning of the era of the Khmer Empire is conventionally dated to 802 CE. In this year, King Jayavarman II had himself declared chakravartin("king of the world", or "king of kings") on Phnom Kulen. The empire ended with the fall of Angkor in the 15th century.

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