Final answer:
The Khmer Empire was the civilization that established an empire in Cambodia and influenced much of Indochina, known for its capital at Angkor and the temple complex of Angkor Wat.
Step-by-step explanation:
The people of Cambodia who established an empire and dominated most of Indochina are known as the Khmer. The Khmer Empire, existing from 802 CE to 1431 CE, was a significant power in Southeast Asia, with its capital at Angkor, which is famed for the sprawling temple complex of Angkor Wat. This empire was influential in spreading both Hinduism and Buddhism throughout the region. Its rulers were seen as incarnations of the Hindu god Vishnu, further asserting the cultural and religious influence of India in Southeast Asia.