| Ontojärvi – Nurmesjärvi | |
| Pushpin Map: | Finland |
| Location: | Kainuu |
| Coords: | 64.1333°N 42°W |
| Inflow: | lakes Lentua, Lammasjärvi, Vieksijärvi |
| Outflow: | river Ontojoki to the lake Iso-Kiimanen |
| Catchment: | Oulujoki |
| Basin Countries: | Finland |
| Area: | 104.572km2 |
| Depth: | 5.76m (18.9feet) |
| Max-Depth: | 29m (95feet) |
| Volume: | 0.602km3 |
| Shore: | 315.87km (196.27miles) |
| Elevation: | 159.2m (522.3feet) |
Ontojärvi–Nurmesjärvi is a rather large lake in the Oulujoki main catchment area in Kainuu, Finland. It is situated in the municipality of Kuhmo.[1] It is the 44th largest lake in the country.[2]