| Sem | |
| Arrondissement: | Foix |
| Canton: | Sabarthès |
| Commune: | Val-de-Sos |
| Insee: | 09286 |
| Postal Code: | 09220 |
| Coordinates: | 42.7686°N 1.5197°W |
| Elevation M: | 960 |
| Elevation Min M: | 825 |
| Elevation Max M: | 2042 |
| Area Km2: | 5.22 |
| Population: | 22 |
| Population Date: | 2021 |
| Population Footnotes: | [1] |
Sem (in French pronounced as /sɛm/) is a former commune in the Ariège department in southwestern France. On 1 January 2019, it was merged into the new commune Val-de-Sos.[2]
The Sem village lies in the Vicdessos valley at 991 meters above sea level. It is an old mining village, tied with the history of the iron mining of Rancié. The stream of Sem forms a huge waterfall (Carraoucou waterfall) and a cone. A big rock called "the dolmen" of Sem was made by a former glacier.
Inhabitants of Sem are called Sémois in French.