| Femmilsjøen | |
| Pushpin Map: | Svalbard |
| Pushpin Map Caption: | Location in Svalbard |
| Location: | Svalbard |
| Coords: | 79.7879°N 15.8503°W |
| Type: | natural freshwater lake |
| Catchment: | 304.4km2 |
| Basin Countries: | Norway |
| Length: | 7.6km (04.7miles) |
| Width: | 1.3km (00.8miles) |
| Area: | 7.56km2 |
| Max-Depth: | 110m (360feet) |
| Elevation: | 26m (85feet) |
| Frozen: | part of year; a glacier permanently covers its eastern end |
Femmilsjøen is a lake in Ny-Friesland at Spitsbergen, Svalbard. The glacier Longstaffbreen debouches into the lake at the eastern end. The western end of the lake is relatively close to Wijdefjorden.[1]