The Âu Việt (Hán tự: 甌越) were a conglomeration of upland tribes living in what is today the mountainous regions of northernmost Vietnam, western Guangdong, and southern Guangxi, China, since at least the 3rd century BC. Its capital was located in what is today the Cao Bằng Province of northeastern Vietnam.
The Âu Việt were also referred to as the Kingdom of Eastern Ou (東甌), descendants of the Yue (state) that had moved to Fujian after its fall. The Western Ou (西甌; Chinese: Xī Ōu; Tây meaning "western"). The Western Ou were one of the Bǎiyuè tribes, with short hair and tattoos, and blackened their teeth and are the ancestors of the upland Tai-speaking minority groups in Vietnam such as the Nùng and Tay, as well as the closely related Zhuang people of Guangxi.
The Âu Việt traded with the Lạc Việt, the inhabitants of the state of Văn Lang, located in the lowland plains to Âu Việt's south, in what is today the Red River Delta of northern Vietnam, until 258 BC or 257 BC, when Thục Phán, the leader of an alliance of Âu Việt tribes, invaded Văn Lang and defeated the last Hùng Vương. He named the new nation "Âu Lạc", proclaiming himself "An Dương Vương" ("King An Dương").
The Qin Dynasty conquered the Chu (state) and abolished the status of the Yue royal descendants. After some years, Shi Huang Di sent 500,000 army to conquer the West Ou, started a three-year guerrilla warfare and killed the Western Ou leader. Before the Han Dynasty, the East and West Ou gain independence again. The Eastern Ou was attacked by the Minyue, and Emperor Wu of Han allowed them to move to between Changjiang and Huaihe. The Western Ou pay tribute to the Nam Viet until it was conquered by the emperor, and it also surrendered. Descendants of these kings lost their status later. Ou (區), Ou (歐) and Ouyang (歐陽) remains in family names.
- Chapuis, Oscar (1995). A History of Vietnam: From Hong Bang to Tu Duc. Greenwood Publishing Group. pp. 13–14. ISBN 0-313-29622-7.
- Vinh Phúc Nguyêñ Historical and cultural sites around Hanoi Thé̂ Giới Publishers, 2000 p24, 25 "became the king both of the Âu Việt and Âu Lạc"
- Anh Tuấn Hoàng Silk for Silver: Dutch-Vietnamese Relations, 1637-1700 Page 12 2007 "people of Lạc Việt."
- Sterling, Eleanor J.; Martha Maud Hurley, Le Duc Minh, Minh Duc Le, Joyce A. Powzyk (2006). Vietnam: a natural history. Yale University Press. p. 28. ISBN 0-300-10608-4.
- Stevenson, John; John Guy, Louise Allison Cort (1997). Vietnamese ceramics: a separate tradition. Art Media Resources with Avery Press. p. 109.
- Huainanzi 卷18, 人間訓