| Caption Map: | Interactive map of the lake |
| Coordinates: | 65.7253°N 13.9739°W |
| Location: | Hemnes Municipality and Hattfjelldal Municipality, Nordland |
| Type: | dammed lake or reservoir |
| Inflow: | Bessedørelva, Bjørkåselva, Gåsvasselva, Hanskvasselva, Jierhtejohke, Krutåga, Laukskardelva, Leirelva, Lilleelva, Raudvasselva, Speelhtejohke, Steikvasselva, Stikkelvikelva, Storelva, Sørdalselva and Tvillelva |
| Outflow: | Røssåga |
| Catchment: | 855km2 |
| Basin Countries: | Norway |
| Date-Flooded: | 1957 |
| Length: | 37km (23miles) |
| Width: | 18km (11miles) |
| Area: | 218.61km2 |
| Depth: | 68m (223feet) (66.5 m before damming) |
| Max-Depth: | 240m (790feet) (231 m before damming) |
| Volume: | 14.8km3 (12.60 km3 before damming) |
| Shore: | 256.37km (159.3miles) |
| Elevation: | 383m (1,257feet) (374 m before damming) |
| Islands: | Røssvassholmen |
| Reference: | NVE[1] |
or is a lake and reservoir in Hattfjelldal Municipality and Hemnes Municipality in Nordland county, Norway. It has been the site of human occupation since the Stone Age. Its area of makes it the second largest lake in Norway by surface area. Without the dam which has regulated the lake since 1957, it would be and the third largest lake in Norway. Its depth is, its volume is estimated at, and its surface elevation is above sea level.
The 17.39km2 island Røssvassholmen is located in the southern part of the lake. it is the largest island in the lake. The highest point on the island reaches above the lake's surface (at top regulation height). The island is Norway's second largest lake-island. The largest island within a lake in Norway is Helgøya, located within the lake Mjøsa.[2]