The Rouran Khaganate (Chinese:柔然; Róurán), also known as Ruanruan or Juan-juan (蠕蠕; Ruǎnruǎn) (or variously Jou-jan, Ruruan, Ju-juan, Ruru, Ruirui, Rouru, Rouruan or Tantan), was a tribal confederation and later state. The Rouran state was undoubtedly multi-ethnic. As the ancient sources regard the Rouran as a separate branch of the Xiongnu Book of Song and Book of Liang connected Rourans to the earlier Xiongnu while the Book of Wei connected them to Proto-Mongolic Donghu. The Rouran supreme rulers used the title of khagan, a popular title borrowed from the Xianbei. The Rouran Khaganate lasted from the late 4th century until the middle 6th century with territory that covered all of modern-day Mongolia and Inner Mongolia, as well as parts of Manchuria in Northeast China, Eastern Siberia, Xinjiang, and Kazakhstan. The Hephthalites were vassals of the Rouran Khaganate until the beginning of the 5th century, with the royal house of Rourans intermarrying with the royal houses of the Hephthalites. The Rouran Khaganate ended when they were defeated by a Göktürk rebellion at the peak of their power, which subsequently led to the rise of the Turks in world history.
Their Khaganate overthrown, some Rouran remnants possibly became Tatars while others possibly migrated west and became the Pannonian Avars (known by such names as Varchonites or Pseudo Avars), who settled in Pannonia (centred on modern Hungary) during the 6th century. These Avars were pursued into the Byzantine Empire by the Göktürks, who referred to the Avars as a slave or vassal people, and requested that the Byzantines expel them. While this Rouran-Avars link remains a controversial theory, a recent DNA study has confirmed the genetic origins of the Avar elite as originating from the Mongolian plains. Other theories instead link the origins of the Pannonian Avars to peoples such as the Uar.
