| Fontaine-sur-Aÿ | |
| Commune Status: | Commune |
| Arrondissement: | Épernay |
| Canton: | Épernay-1 |
| Insee: | 51256 |
| Postal Code: | 51160 |
| Mayor: | Alain-Louis Gourdy[1] |
| Term: | 2022 - 2026 |
| Intercommunality: | Grande Vallée de la Marne |
| Coordinates: | 49.0828°N 4.0733°W |
| Elevation M: | 90 |
| Area Km2: | 7.72 |
Fontaine-sur-Ay (in French pronounced as /fɔ̃tɛn syʁ aj/, literally Fontaine on Ay; also Fontaine-sur-Aÿ) is a commune in the Marne department in north-eastern France.