| Iwaya Dam | |
| Name Official: | 岩屋ダム |
| Dam Crosses: | Maze River |
| Location: | Gero, Gifu Prefecture, Japan |
| Dam Length: | 366.0 meters |
| Dam Height: | 127.5 meters |
| Construction Began: | 1966 |
| Opening: | 1976 |
| Res Capacity Total: | 173,500,000 m3 |
| Res Catchment: | 1,734.9 km2 |
| Res Surface: | 424 hectares |
| Coordinates: | 35.7611°N 137.1572°W |
| Plant Capacity: | 28.8 MW |
The is a dam in the city of Gero, Gifu Prefecture, Japan on the Maze River, part of the Kiso River system. The dam is a rockfill dam with a height of 127 meters and was constructed as a multipurpose dam for flood control, supply of municipal and industrial water, irrigation water and hydroelectric power generation. The reservoir created by the dam supplies the Chubu Electric Power Company's Mazegawa No.1 Power plant with a capacity of 288 MW hydroelectric power station.[1]
157 households were flooded during the construction of the dam.