Cambodia ( ; Khmer: កម្ពុជា; UNGEGN: Kâmpŭchéa), officially the Kingdom of Cambodia (Khmer: ព្រះរាជាណាចក្រកម្ពុជា; UNGEGN: Preâh Réachéanachâkr Kâmpŭchéa), is a country in Mainland Southeast Asia, spanning an area of 181,035 square kilometres (69,898 square miles), 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.
In 802 AD, Jayavarman II declared himself king, uniting the warring Khmer princes of Chenla under the name "Kambuja". This marked the beginning of the Khmer Empire. The Indianised kingdom facilitated the spread of first Hinduism and then Buddhism to Southeast Asia and undertook religious infrastructural projects throughout the region. In the fifteenth century, Cambodia experienced a decline of power, and in 1863, it became a protectorate of France. After a period of Japanese occupation during the Second World War, Cambodia gained independence in 1953. The Vietnam War extended into the country in 1965 via the Ho Chi Minh and Sihanouk trails. A 1970 coup installed the US-aligned Khmer Republic, which was overthrown by the Khmer Rouge in 1975. The Khmer Rouge ruled the country and carried out the Cambodian genocide from 1975 until 1979, when they were ousted in the Cambodian–Vietnamese War. The Vietnamese-occupied People's Republic of Kampuchea became the de facto government. Following the 1991 Paris Peace Accords which formally ended the war with Vietnam, Cambodia was governed by a United Nations mission (1992–93). The UN withdrew after holding elections in which around 90% of the registered voters cast ballots. The 1997 coup d'état consolidated power under Prime Minister Hun Sen and the Cambodian People's Party (CPP). While constitutionally a multi-party state, CPP dominates the political system and dissolved its main opposition party in 2017, making Cambodia a de facto one-party state.The United Nations designates Cambodia as a least developed country. Cambodia is a member of the United Nations, ASEAN, the RCEP, the East Asia Summit, the WTO, the Non-Aligned Movement and La Francophonie. Cambodia is a dialogue partner of the Shanghai Cooperation Organization. Agriculture remains the dominant economic sector, with growth in textiles, construction, garments, and tourism leading to increased foreign investment and international trade. Cambodia is considered among the most vulnerable countries to climate change.