| Bailly | |
| Commune Status: | Commune |
| Image Coat Of Arms: | Blason Bailly 78.svg |
| Arrondissement: | Versailles |
| Canton: | Le Chesnay-Rocquencourt |
| Insee: | 78043 |
| Postal Code: | 78870 |
| Mayor: | Jacques Alexis[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | CA Versailles Grand Parc |
| Coordinates: | 48.842°N 2.078°W |
| Elevation M: | 181 |
| Elevation Min M: | 92 |
| Elevation Max M: | 182 |
| Area Km2: | 6.53 |
Bailly (in French pronounced as /baji/) is a commune in the Yvelines department in north-central France.