Juan Juan (wg), Ruanruan (py), Ru Ru (py) or Rouran 柔然 (py) was the name of a confederacy of nomadic tribes on the northern borders of China proper from late 4th century until late 6th century. The term Rouran (柔然) was a Chinese language transciption of the pronunciation of the name the confedarcy used to refer to itself. Some readers consider the Korean pronunciation Yuyon a more archaic form and closer to the original pronunciation. The derogatory term Juan Juan (wg) or Ruan Ruan (py) (蠕蠕 lit. meaning "Wriggling insects") and Ru Ru (茹茹 lit. meaning "Fodder") remained in modern usage despite being derived by Emperor Taiwu of Northern Wei who waged war against and intended to intimidate the confederacy.
Little is known of their ruling elite, which the Weishu cited as an offshoot of the Xianbei. The Juan Juan subdued modern regions of Xinjiang, Mongolia, Central Asia and parts of Siberia and Manchuria since late 4th century. Their frequent intervention and invasions had profoundly affected neighboring countries although its power was broken by a newer alliance of Gokturks, the Chinese Northern Qi and Northern Zhou dynasties and tribes in Central Asia in 560s. The Chinese Northern Wei Dynasty, for instance, had established six major garrisons bordering the Juan Juan, which later became the foci of native Xianbei upraising against sinicized Xianbei in early 6th century.
Analogy of the Xiongnu-Hun relationship has once rendered a gross generalization that the Juan Juan re-emerged in Europe as the Avars. However the Avars had well established in Europe in 550s whereas the Juan Juan still appeared in Chinese sources in 560s. Nonetheless according to the story that the Uar (original source & chinese character missing), one of the tribes under this confederacy, was placed at the head of the Uighurs in 460, an element of the European Avars may have been, at least for a little while, a small part of the Juan Juan confederacy.