| Le Mesnil-Opac | |
| Arrondissement: | Saint-Lô |
| Canton: | Condé-sur-Vire |
| Insee: | 50316 |
| Postal Code: | 50860 |
| Commune: | Moyon Villages |
| Coordinates: | 49.0136°N -1.0964°W |
| Elevation Min M: | 65 |
| Elevation Max M: | 161 |
| Area Km2: | 5.58 |
| Population: | 249 |
| Population Date: | 2019 |
| Population Footnotes: | [1] |
| Demonym: | Opaciens |
Le Mesnil-Opac (pronounced as /fr/) is a former commune in the Manche department in Normandy in north-western France. On 1 January 2016, it was merged with the new commune of Moyon Villages.[2]