| Mantasoa Dam | |
| Location Map: | Madagascar |
| Coordinates: | -19.0179°N 47.8498°W |
| Country: | Madagascar |
| Location: | Mantasoa, Analamanga Region |
| Purpose: | Power, water supply |
| Status: | O |
| Construction Began: | 1937 |
| Owner: | Jirama |
| Dam Type: | Buttress |
| Dam Crosses: | Varahina-North River |
| Dam Length: | 122m (400feet) |
| Dam Height: | 20m (70feet) |
| Res Name: | Lake Mantasoa |
| Res Capacity Total: | 125000000m2 |
| Res Surface: | 20km2 |
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 French contractors between 1937 and 1938. It creates Lake Mantasoa which has a surface area of 20km2. The dam itself is made of 8000m2 of concrete and has a reinforced buttress design.[1] Water released from the dam supplies a regulated flow to hydroelectric power station at the Antelomita Dams downstream. A saddle dam on the north side of the Mantosoa reservoir regulates water flow into the Mandraka River for the Mandraka Dam downstream.[2] [3]