The đàn nhị (Vietnamese: [ɗâːn ɲîˀ], also called đàn cò, is a Vietnamese bowed string instrument with two strings. The word nhị means "two" in Vietnamese. Its sound box is generally covered on one end with snakeskin.
It is related to the huqin family of instruments of China. Some Austroasiatic groups in Vietnam also have their version of Dan Co. (ex: Mường have Cò Kè, Chứt have T'rơbon, Khua have Karong and Khmer have Tro)