| Castin | |
| Commune Status: | Commune |
| Image Coat Of Arms: | Blason ville fr Castin (32).svg |
| Arrondissement: | Auch |
| Canton: | Gascogne-Auscitaine |
| Insee: | 32091 |
| Postal Code: | 32810 |
| Mayor: | Pierrette Luche[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | CA Grand Auch Cœur Gascogne |
| Coordinates: | 43.6919°N 0.5472°W |
| Elevation M: | 235 |
| Elevation Min M: | 148 |
| Elevation Max M: | 266 |
| Area Km2: | 11.22 |
Castin (pronounced as /fr/) is a commune in the Gers department in southwestern France.