The Orco (Piemontese: Eva d'òr, that is Water of gold; Latin: Orgus) is an Italian river. It originates in the Piedmontese slopes of Gran Paradiso, and after about 100 km (62 mi) reaches the Po River near Chivasso. Its drainage basin is home to the most important complex of hydropower in Piedmont, consisting of five dams: Agnel, Serrù, Ceresole, Piantonetto, Valsoera, and numerous turbines.
The Orco is known also for its gold-bearing sand, extracted already in antiquity. Even today there is a certain activity, on an amateur level, searching for grains of gold.