The largest of the ethnic groups in Cambodia are the Khmer, who comprise 95.8% of the total population and primarily inhabit the lowland Mekong subregion and the central plains. The Khmer historically have lived near the lower Mekong River in a contiguous arc that runs from the southern Khorat Plateau where modern-day Thailand, Laos and Cambodia meet in the northeast, stretching southwest through the lands surrounding Tonle Sap lake to the Cardamom Mountains, then continues back southeast to the mouth of the Mekong River in southeastern Vietnam.

Cambodia, officially the Kingdom of Cambodia, is a country in Southeast Asia on the Indochinese Peninsula, spanning an area of 181,035 square kilometres, bordered by Thailand to the northwest, Laos to the north, Vietnam to the east, and the Gulf of Thailand to the southwest. The capital and most populous city is Phnom Penh.