Ljungan (Jamtlandic: Jångna or Aoa, from Old Norse *Oghn "the dreadful"[3]) is a 322 kilometer long river in Sweden.

The river runs through the Swedish counties of Jämtland and Västernorrland.

Several hydropower plants are located along the river.

A pathogenic virus of the viral family which includes polio and hepatitis A was isolated from a bank vole near the Ljungan river in the mid-1990s, and named Ljungan virus.

This article related to a river in Sweden is a stub.