| Oncy-sur-École | |
| Commune Status: | Commune |
| Image Coat Of Arms: | Blason ville fr Oncy-sur-École (Essonne).svg |
| Coordinates: | 48.3825°N 2.4739°W |
| Insee: | 91463 |
| Postal Code: | 91490 |
| Arrondissement: | Évry |
| Canton: | Mennecy |
| Intercommunality: | CC des 2 Vallées |
| Mayor: | Bruno Delecour[1] |
| Term: | 2020 - 2026 |
| Elevation Min M: | 62 |
| Elevation Max M: | 132 |
| Area Km2: | 5.37 |
Oncy-sur-École (in French pronounced as /ɔ̃si syʁ ekɔl/) is a commune in the Essonne department in Île-de-France in northern France.
Inhabitants of Oncy-sur-École are known as Oncéens.
Painter Simon Mathurin Lantara was a native of the commune.