| Mjøsundvatnet | |
| Caption Map: | Interactive map of the lake |
| Coordinates: | 64.8136°N 12.1148°W |
| Location: | Namsos and Nærøysund, Trøndelag |
| Basin Countries: | Norway |
| Area: | 8.76km2 |
| Reference: | NVE[1] |
Mjøsundvatnet[2] is a lake in Namsos Municipality and Nærøysund Municipality in Trøndelag county, Norway. The 8.76km2 lake lies in the far northern part of Namsos, and it extends a short distance into Nærøysund on both ends. The lake is accessible by road from Salsbruket in Nærøysund Municipality.[3]