| Mathiassen Mountain | |
| Elevation M: | 611 |
| Elevation Ref: | [1] |
| Prominence M: | 611 |
| Isolation Km: | 343.43 |
| Range: | Porsild Mountains |
| Location: | Kivalliq Region Nunavut, Canada |
| Map: | Canada Nunavut#Canada |
| Label Position: | left |
| Coordinates: | 64.8303°N -83.6022°W |
Mathiassen Mountain is a mountain summit, the tallest on Southampton Island, in the Canadian territory of Nunavut.