| Hémonstoir | |
| Native Name: | Henvoustoer |
| Commune Status: | Commune |
| Coordinates: | 48.1594°N -2.8297°W |
| Insee: | 22075 |
| Postal Code: | 22600 |
| Arrondissement: | Saint-Brieuc |
| Canton: | Guerlédan |
| Mayor: | Benoît Larvor[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | Loudéac Communauté - Bretagne Centre |
| Elevation Min M: | 77 |
| Elevation Max M: | 166 |
| Area Km2: | 14.03 |
Hémonstoir (in French pronounced as /emɔ̃stwaʁ/; Breton: Henvoustoer; Gallo: Hémontoèr) is a commune in the Côtes-d'Armor department of Brittany in northwestern France.
Inhabitants of Hémonstoir are called hémonstoiriens in French.