| Saint-Mars-sous-Ballon | |
| Arrondissement: | Le Mans |
| Canton: | Bonnétable |
| Insee: | 72301 |
| Postal Code: | 72290 |
| Commune: | Ballon-Saint-Mars |
| Coordinates: | 48.1733°N 0.2464°W |
| Elevation Min M: | 54 |
| Elevation Max M: | 130 |
| Area Km2: | 18.2 |
| Population: | 871 |
| Population Date: | 2018 |
| Population Footnotes: | [1] |
Saint-Mars-sous-Ballon (pronounced as /fr/, literally Saint-Mars under Ballon) is a former commune in the Sarthe department in the region of Pays de la Loire in north-western France. On 1 January 2016, it was merged into the new commune of Ballon-Saint-Mars.[2] Its population was 871 in 2018.[1]