| Messac | |
| Native Name: | Mezeg |
| Image Coat Of Arms: | Blason ville fr Messac (Ille-et-Vilaine).svg |
| Coordinates: | 47.8256°N -1.8072°W |
| Insee: | 35176 |
| Postal Code: | 35480 |
| Arrondissement: | Redon |
| Canton: | Redon |
| Commune: | Guipry-Messac |
| Elevation Min M: | 3 |
| Elevation Max M: | 89 |
| Area Km2: | 41.64 |
| Population: | 3204 |
| Population Date: | 2018 |
| Population Footnotes: | [1] |
Messac (in French pronounced as /mesak/; Breton: Mezeg; Gallo: Meczac) is a former commune in the Ille-et-Vilaine department of Brittany in northwestern France. On 1 January 2016, it was merged into the new commune Guipry-Messac.[2]
Inhabitants of Messac are called Messacois in French.