|Native to||Rouran Khaganate|
|Region||Mongolia and northern China|
|Era||4th century CE – 6th century CE|
Alexander Vovin (2004, 2010) considers the Ruan-ruan language to be an extinct non-Altaic language that is not related to any modern-day language (i.e., a language isolate) and is hence unrelated to Mongolic. Vovin (2004) notes that Old Turkic had borrowed some words from an unknown non-Altaic language that may have been Ruan-ruan.
- no mid vowels
- initial l-
- final consonantal cluster -nd
- küskü – 'rat'
- ud – 'ox'
- luu – 'dragon' < Middle Chinese luŋ – 'dragon'
- yund – 'horse'
- laγzïn – 'pig'
- qaγan – 'emperor'
- qan – 'khan'
- qaγatun – 'empress'
- qatun – 'khan's wife'
- aq – 'dung'
- and – 'oath'
- Vovin, Alexander 2004. ‘Some Thoughts on the Origins of the Old Turkic 12-Year Animal Cycle.’ Central Asiatic Journal 48/1: 118–32.
- Vovin, Alexander. 2010. Once Again on the Ruan-ruan Language. Ötüken’den İstanbul’a Türkçenin 1290 Yılı (720–2010) Sempozyumu From Ötüken to Istanbul, 1290 Years of Turkish (720–2010). 3–5 Aralık 2010, İstanbul / 3–5 December 2010, İstanbul: 1–10.