Mantasoa Dam is a buttress dam on the Varahina-North River, a tributary of the Ikopa River, near Mantasoa in the Analamanga Region of Madagascar. The dam was constructed by the French Business Company between 1937 and 1938. It creates Lake Mantasoa which has a surface area of 20 km2 (7.7 sq mi). The dam itself is made of 8,000 m3 (10,000 cu yd) of concrete and has a reinforced buttress design.