Cambodia or Khmer is a country located in the southern portion of the Indochina peninsula in Southeast Asia. It is 181,035 square kilometres (69,898 square miles) in the area, bordered by Thailand to the northwest, Laos to the northeast, Vietnam to the east and the Gulf of Thailand to the southwest. The sovereign state of Cambodia has a population of over 16 million. The official religion is Theravada Buddhism, practised by approximately 95 percent of the population. The country's minority groups include Vietnamese, Chinese, Chams, and 30 hill tribes. The capital and largest city are Phnom Penh, the political, economic and cultural centre of Cambodia. The kingdom is an elective constitutional monarchy with a monarch, currently Norodom Sihamoni, chosen by the Royal Throne Council as head of state. The head of government is the Prime Minister, currently Hun Sen, the longest serving non-royal leader in Southeast Asia, ruling Cambodia since 1985.
In 802 CE, Jayavarman II declared himself king, uniting the warring Khmer princes of Chenlaunder under the name "Kambuja". This marked the beginning of the Khmer Empire, which flourished for over 600 years, allowing successive kings to control and exert influence over much of Southeast Asia and accumulate immense power and wealth. The Indianised kingdom facilitated the spread of first Hinduism and then Buddhism to much of Southeast Asia and undertook many religious infrastructural projects throughout the region, including the construction of more than 1,000 temples and monuments in Angkor alone. Angkor Wat is the most famous of these structures and is designated as a World Heritage Site. After the fall of Angkor to Ayutthaya in the 15th century, a reduced and weakened Cambodia was then ruled as a vassal state by its neighbours. In 1863, Cambodia became a protectorate of France, which doubled the size of the country by reclaiming the north and west from Thailand.
Cambodia gained independence in 1953. The Vietnam War extended into the country with the US bombing of Cambodia from 1969 until 1973. Following the Cambodian coup of 1970 which installed the right-wing pro-US Khmer Republic, the deposed king gave his support to his former enemies, the Khmer Rouge. The Khmer Rouge emerged as a major power, taking Phnom Penh in 1975 and later carrying out the Cambodian genocide from 1975 until 1979, when they were ousted by Vietnam and the Vietnamese-backed People's Republic of Kampuchea, supported by the Soviet Union in the Cambodian–Vietnamese War (1979–91). Following the 1991 Paris Peace Accords, Cambodia was governed briefly by a United Nations mission (1992–93). The UN withdrew after holding elections in which around 90 percent of the registered voters cast ballots. The 1997 factional fighting resulted in the ousting of the government by Prime Minister Hun Sen and the Cambodian People's Party, who remain in power as of present.