| Casteil | |
| Native Name: | Castell de Vernet |
| Commune Status: | Commune |
| Image Coat Of Arms: | Blason ville fr Casteil 66.svg |
| Arrondissement: | Prades |
| Canton: | Le Canigou |
| Insee: | 66043 |
| Postal Code: | 66820 |
| Mayor: | Olivier Chauveau[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | Conflent-Canigó |
| Coordinates: | 42.5319°N 2.3942°W |
| Elevation M: | 750 |
| Elevation Min M: | 697 |
| Elevation Max M: | 2721 |
| Area Km2: | 29.83 |
Casteil (pronounced as /fr/; ca|Castell de Vernet) is a commune in the Pyrénées-Orientales department in southern France, part of the historical Conflent comarca. The abbey Martin-du-Canigou is located above Casteil.
Casteil is located in the canton of Le Canigou and in the arrondissement of Prades.