Vietnamese Cambodians refers to ethnic group of Vietnamese who live in Cambodia or it refers to Vietnamese who are of full or partial Khmer descent. According to Cambodian sources, in 2013, about 15,000 Vietnamese people live in Cambodia. A Vietnamese source stated that 156,000 people live in Cambodia, while the actual number could be somewhere between 400,000 and one million people, according to independent scholars. They mostly reside in southeastern parts of Cambodia bordering Vietnam or on houseboats in the Tonlé Sap lake and Mekong rivers. The first Vietnamese came to settle modern-day Cambodia from the early 19th century during the era of the Nguyễn lords and most of the Vietnamese came to Cambodia during the periods of French colonial administration and the People's Republic of Kampuchea administration. During the Khmer Republic and Khmer Rouge governments in the 1970s under the Pol Pot regime, the Vietnamese amongst others were targets of mass genocides; thousands of Vietnamese were killed and many more sought refuge in Vietnam.
Ethnic relations between the Cambodians and Vietnamese are complex, where despite engagement and collaboration between the two countries of Cambodia and Vietnam, Vietnamese have been the target of xenophobic attacks by opposition political parties against Hun Sen's policies since the 1990s. Many of the stateless Vietnamese residents face difficulties in getting access to education, employment, and housing. Although xenophobic sentiments have been a continuing source of concern, they have not been a barrier towards neighbourly ties within the context of Southeast Asia and other international affairs.
History
Relations between Cambodia and Vietnam date back to when Chey Chettha II, in order to balance the influence of the Siamese forces, which had devastated the previous capital at Longvek during the reign of his father, had struck an alliance with Vietnam and married Princess Nguyễn Phúc Ngọc Vạn, a daughter of Lord Nguyễn Phúc Nguyên, in 1618. In return, the king had granted the Vietnamese the right to establish settlements in Mô Xoài (now Bà Rịa), in the region of Prey Nokor—which they colloquially referred to as Sài Gòn, and which later became Ho Chi Minh City. Vietnamese settlers first entered the Mekong and the Prey Nokor area (later Saigon) from the 1620s onwards. The region then as now is known to the Cambodians as Kampuchea Krom but by cession and conquest (Vietnamese expansion to the South, dubbed Nam Tiến), the area came under Vietnamese control. Under the reign of Chey Chettha II, Cambodia formally ceded the eastern portion to the Nguyễn lords.
With the unification Vietnam under Emperor Gia Long, the Court of Huế asserted its hegemony in 1813 and sent 10,000 troops to Phnom Penh. The Cambodian court was split into rival factions vying for power and some members of the Cambodian royal sought the support of the Vietnamese, thus implanting Vietnamese power within the kingdom. Favors were granted to allow more Vietnamese settlers and by the reign of Emperor Minh Mạng, Vietnam chose to impose its rule directly, relegating the Cambodian court to a minor role. Administrative renaming of town and provinces was carried out while Vietnamese customs were forced upon the Cambodian populace. The heavy-handed policies stirred resentment among the Cambodian populace, provoking protracted insurgency and unrest. Vietnam was forced to withdraw, accepting the restoration of the royal candidate Ang Duong as the Cambodian king. Vietnam nonetheless joined Siam to hold Cambodia in joint vassalage.
In 1880 with the establishment of the French colonial administration, Cambodia joined Vietnam as part of French Indochina, the status to Vietnamese residents in Cambodia was formally legalized. Over the next fifty years, large numbers of Vietnamese migrated to Cambodia. Population censuses conducted by the French recorded an increase in the Vietnamese population from about 4,500 in the 1860s to almost 200,000 at the end of the 1930s. When the Japanese invaded Indochina in 1940, Vietnamese nationalists in Cambodia launched a brief but unsuccessful attempt to attack the French colonial administrators.
With independence in 1954, Cambodia legislated a citizenship law based on knowledge in the Khmer language and national origin; this effectively excluded most Vietnamese and Chinese Cambodians. At the grassroot level, Vietnamese also faced occasional cases of violent intimidation from the Cambodians. During a Sangkum congress in 1962, politicians debated on the issue of citizenship on Cambodia's ethnic minorities and a resolution was passed not to grant naturalization of Vietnamese residents.