Rouran, also called Ruanruan, Ruan-ruan or Juan-juan, is an unclassified extinct language of Mongolia and Inner Mongolia, spoken in the Rouran Khaganate from the 4th to the 6th centuries AD. The Rouran state was undoubtedly multi-ethnic, but there is no definite evidence as to their language. The received view is that the relationships of the language remain a puzzle.