| Castagnac | |
| Commune Status: | Commune |
| Arrondissement: | Muret |
| Canton: | Auterive |
| Insee: | 31111 |
| Postal Code: | 31310 |
| Mayor: | Marie-Josée Varela[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | Volvestre |
| Coordinates: | 43.225°N 1.351°W |
| Elevation M: | 351 |
| Elevation Min M: | 217 |
| Elevation Max M: | 363 |
| Area Km2: | 10.77 |
Castagnac (in French pronounced as /kastaɲak/; Occitan (post 1500);: Castanhac) is a commune in the Haute-Garonne department in southwestern France.
The Lèze forms most of the commune's north-eastern border. There are numerous hiking routes.[2]
The commune is bordered by five other communes, three of them is in Haute-Garonne, and two of them is in Ariège: Latrape to the west, Canens to the south, Massabrac to the southeast, and finally by the department of Ariège to the north and east by the communes of Lézat-sur-Lèze to the north and Saint-Ybars to the east.