The Lousios (Greek: Λούσιος) is a river and a gorge in western Arcadia that stretches from Karytaina north to Dimitsana in Greece. The river begins near Lykochori and flows through the Lousios Gorge. The river is treacherous and flows rapidly. It empties into the Alfeios 2.5 km northwest of Karytaina and south of Atsicholos.The river forms a deep, narrow gorge. Its length is approximately 15 km from north to south and its width is approximately 2 km wide.