| Seissan | |
| Commune Status: | Commune |
| Image Coat Of Arms: | Blason ville fr Seissan (Gers).svg |
| Arrondissement: | Mirande |
| Canton: | Astarac-Gimone |
| Insee: | 32426 |
| Postal Code: | 32260 |
| Mayor: | François Rivière[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | Val de Gers |
| Coordinates: | 43.4933°N 0.5939°W |
| Elevation M: | 187 |
| Elevation Min M: | 168 |
| Elevation Max M: | 283 |
| Area Km2: | 18.56 |
Seissan (in French pronounced as /sɛsɑ̃/; Occitan (post 1500);: Sheishan) is a commune in the Gers department in southwestern France.