| Atnsjøen | |
| Pushpin Map: | Innlandet#Norway |
| Pushpin Label Position: | bottom |
| Pushpin Map Caption: | Location of the lake |
| Coordinates: | 61.8753°N 10.1769°W |
| Location: | Stor-Elvdal and Sør-Fron, Innlandet |
| Basin Countries: | Norway |
| Area: | 5km2 |
| Reference: | NVE[1] |
Atnsjøen is a lake in Innlandet county, Norway. The 5km2 lake lies along the border of the municipalities of Sør-Fron and Stor-Elvdal, just east of Rondane National Park. The Norwegian County Road 27 runs along the eastern shoreline of the entire lake. The village of Sollia lies about to the southeast of the lake.