Cachapoal River is tributary river of the Rapel River in Chile located in the Libertador General Bernardo O'Higgins Region. The river gives its name to the Cachapoal Province.
The valley takes its name from the Cachapoal River that flows through Rapel Valley along with its tributaries, the Claro and Cortaderal rivers. All these watercourses flow into Rapel Lake.
The climate of the valley is temperate and consistently Mediterranean, sheltered by the coastal range from the cooling influences of the Pacific Ocean.
Coordinates: 34°16′29″S 71°26′05″W / 34.27472°S 71.43472°W