| Mézy-sur-Seine | |
| Commune Status: | Commune |
| Image Coat Of Arms: | Blason ville fr Mézy-sur-Seine (Yvelines).svg |
| Arrondissement: | Mantes-la-Jolie |
| Canton: | Les Mureaux |
| Insee: | 78403 |
| Postal Code: | 78250 |
| Mayor: | Fabrice Zuccarelli[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | CU Grand Paris Seine et Oise |
| Coordinates: | 49.0028°N 1.8822°W |
| Elevation M: | 65 |
| Elevation Min M: | 17 |
| Elevation Max M: | 155 |
| Area Km2: | 4.76 |
Mézy-sur-Seine (in French pronounced as /mezi syʁ sɛn/, literally Mézy on Seine) is a commune in the Yvelines department in the Île-de-France region in north-central France.