Nen (nŭn) or Nonni (nôn´nē), river, 740 mi (1,191 km) long, rising in the Yilehuli (Ilkuri) Mts., N Heilongjiang prov., NE China, and flowing south along the east side of the Da Hinggan (Great Khingan) range to the Songhua River; forms part of the Heilongjiang-Jilin provincial border. Though frozen from November to April, the river and its valley form an important trade artery. It is navigable for shallow-draft vessels along most of its length; a railroad follows its valley.

Nen: see Nene, river, England.