| Castelnau-Barbarens | |
| Commune Status: | Commune |
| Image Coat Of Arms: | Blason ville fr Castelnau-Barbarens (Gers).svg |
| Arrondissement: | Auch |
| Canton: | Astarac-Gimone |
| Insee: | 32076 |
| Postal Code: | 32450 |
| Mayor: | Michel Burgan[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | CA Grand Auch Cœur Gascogne |
| Coordinates: | 43.5772°N 0.7247°W |
| Elevation M: | 295 |
| Elevation Min M: | 157 |
| Elevation Max M: | 291 |
| Area Km2: | 42.37 |
Castelnau-Barbarens (Gascon: Castèthnau Barbarens) is a commune in the Gers department in southwestern France.