The Loussios or 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 into the Lousios Gorge. The river is treacherous and flows rapidly. It empties into the Alfeios 2.5 km northwest of Karytaina nad south of Atsicholos.
The gorge includes the Loussios river. Its length is approximately 15 km from north to south and its width is approximately 2 km wide. The gorge is very popular amongst hikers. A the end of the gorge finds the town of Dimitsana. At the other side of the gorge is the ancient city of Gortys with the temple of Asclepius. The gorge is encircled with the Karytaina-Dimitsana Road to the east and several rural roads and trails as well as zig-zag roads. The gorge can be viewable from the east side. Much of the gorge are heavily forested, the remainder are treacherous cliffs. One of the roads crossing the south of the gorge is the road linking Karytaina and Atsicholos.
During rainy days, the gorge is dangerous to cross and is not permitted.