| Moncassin | |
| Commune Status: | Commune |
| Arrondissement: | Mirande |
| Canton: | Mirande-Astarac |
| Insee: | 32263 |
| Postal Code: | 32300 |
| Mayor: | Jean-Claude Verdier[1] |
| Term: | 2020 - 2026 |
| Coordinates: | 43.4544°N 0.4803°W |
| Elevation M: | 169 |
| Elevation Min M: | 179 |
| Elevation Max M: | 283 |
| Area Km2: | 13.93 |
Moncassin (in French pronounced as /mɔ̃kasɛ̃/; Occitan (post 1500);: Montcassin) is a commune in the Gers department in southwestern France.
The Petite Baïse flows north through the middle of the commune and forms parts of its northern border.