| Lasserre | |
| Commune Status: | Commune |
| Arrondissement: | Saint-Girons |
| Canton: | Portes du Couserans |
| Insee: | 09158 |
| Postal Code: | 09230 |
| Mayor: | Alain Bari[1] |
| Term: | 2020 - 2026 |
| Coordinates: | 43.0703°N 1.1711°W |
| Elevation M: | 574 |
| Elevation Min M: | 360 |
| Elevation Max M: | 576 |
| Area Km2: | 8.47 |
Lasserre (in French pronounced as /lasɛʁ/; Occitan (post 1500);: La Sèrra) is a commune in the Ariège department in southwestern France.
It was the home of Alexander Grothendieck for over ten years until his death.