| Gadancourt | |
| Image Coat Of Arms: | Blason Gadancourt 95.svg |
| Coordinates: | 49.0969°N 1.8578°W |
| Arrondissement: | Pontoise |
| Canton: | Vauréal |
| Commune: | Avernes |
| Elevation Min M: | 87 |
| Elevation Max M: | 141 |
| Area Km2: | 4.68 |
| Population: | 83 |
| Population Date: | 2015 |
| Population Footnotes: | [1] |
| Insee: | 95259 |
| Postal Code: | 95450 |
Gadancourt (in French pronounced as /ɡadɑ̃kuʁ/) is a former commune in the Val-d'Oise department in Île-de-France in northern France. On 1 January 2018, it was merged into the commune of Avernes.[2]