| Marcilly-sur-Seine | |
| Commune Status: | Commune |
| Arrondissement: | Épernay |
| Canton: | Vertus-Plaine Champenoise |
| Insee: | 51343 |
| Postal Code: | 51260 |
| Mayor: | Benoît Bassac[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | Sézanne-Sud Ouest Marnais |
| Coordinates: | 48.5575°N 3.71°W |
| Elevation M: | 70 |
| Area Km2: | 10.01 |
Marcilly-sur-Seine (pronounced as /fr/, literally Marcilly on Seine) is a commune in the Marne department in north-eastern France. It is near the confluence of the Aube and the Seine.