Lyngdalen is a valley in Agder county, Norway. The 60-kilometre (37 mi) long valley runs north–south through the municipalities of Hægebostad and Lyngdal. The valley follows the river Lygna from the mountain plateaus in northern Hægebostad to the Lyngdalsfjorden, just south of the town of Lyngdal. The villages of Kvås, Snartemo, and Tingvatn are all located in the valley. The long, narrow lake Lygne is also located in the valley.