| Grønfjellåga | |
| Pushpin Map: | Nordland#Norway |
| Pushpin Map Caption: | Location of the river |
| Subdivision Type1: | Country |
| Subdivision Name1: | Norway |
| Subdivision Type2: | County |
| Subdivision Name2: | Nordland |
| Subdivision Type3: | Municipalities |
| Subdivision Name3: | Rana Municipality |
| Length: | 17km (11miles) |
| Source1: | Kopparvassdalen valley |
| Source1 Location: | Rana, Norway |
| Source1 Coordinates: | 66.333°N 14.8717°W |
| Mouth: | Ranelva river |
| Mouth Location: | Nevernes, Rana, Norway |
| Mouth Coordinates: | 66.3733°N 14.5924°W |
Grønfjellåga (lit. "the river of the green mountain") is a river in the municipality of Rana in Nordland county, Norway. The 17km (11miles) long river's source is the lakes Kallvatnet and Kopparvatnet. It then flows through the Grønfjelldalen valley while absorbing several smaller rivers, before it flows out as a tributary to the river Ranelva at the Dunderforsen waterfall (also called Stupforsen).[1]
These photos are from a place east of Stupforsen: