| Flensjøen | |
| Pushpin Map: | Trøndelag#Innlandet#Norway |
| Pushpin Label Position: | top |
| Pushpin Map Caption: | Location of the lake |
| Coordinates: | 62.3849°N 11.7681°W |
| Location: | Innlandet and Trøndelag |
| Basin Countries: | Norway |
| Area: | 3.41km2 |
| Reference: | NVE |
Flensjøen is a lake on the border of Innlandet and Trøndelag counties in Norway. The 3.41km2 lake lies in the municipalities of Røros (in Trøndelag county) and Os (in Innlandet county). The lake lies about southeast of the town of Røros, about half-way between the lakes Korssjøen and Femunden, and about south of Håsjøen.[1]