| Kostonjärvi | |
| Pushpin Map: | Finland |
| Location: | Taivalkoski |
| Coords: | 65.7833°N 55°W |
| Inflow: | Kynsijoki river |
| Outflow: | Kostonjoki river |
| Catchment: | Iijoki |
| Basin Countries: | Finland |
| Area: | 43.69km2 |
| Depth: | 5.09m (16.7feet) |
| Max-Depth: | 17m (56feet) |
| Volume: | 0.222km3 |
| Shore: | 71.1km (44.2miles) |
| Elevation: | 231.6m (759.8feet) |
| Frozen: | November–May |
Kostonjärvi is a medium-sized lake in the Iijoki main catchment area. It is located in Taivalkoski municipality, in the Northern Ostrobothnia region in Finland.[1] The surface elevation on the lake varies almost 5 meter due to the power production.[2]