Lygna or Lyngdalselva is a river in Agder county, Norway. The river runs from the mountains in northern Hægebostad municipality, through the Lyngdalen valley to the municipality of Lyngdal to its mouth at Alleen, where it runs into Lyngdalsfjorden. Lygna has a discharge of , and a drainage basin covering . The river is called the StorÃÂ¥ni north of the lake Lygne. The river passes the villages of Tingvatn, Snartemo, and KvÃÂ¥s as well as the town of Lyngdal.