The Âu Việt (Hán tự: 甌越; Pinyin: Ōu Yuè) were a conglomeration of upland tribes living in what is today the mountainous region 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 Bang Province of northeastern Vietnam.
The Âu Việt were also referred to as Tây Âu (西甌; ; Tây meaning "western"), and were considered to be one of the Hundred Yue tribes. They had short hair and tattoos, and blackened their teeth. They are considered to have been the ancestors of the upland Tai-speaking minority groups in Vietnam such as the Nung 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, which was 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 the alliance of Âu Việt tribes, invaded Văn Lang and defeated the last Hùng Vương. He united the two kingdoms, naming the new nation "Âu Lạc," and proclaiming himself king An Dương Vương.