| Longaulnay | |
| Commune Status: | Commune |
| Image Coat Of Arms: | Blason ville fr Longaulnay 35.svg |
| Coordinates: | 48.3108°N -1.9383°W |
| Insee: | 35156 |
| Postal Code: | 35190 |
| Arrondissement: | Saint-Malo |
| Canton: | Combourg |
| Mayor: | David Buisset[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | Bretagne Romantique |
| Elevation Min M: | 65 |
| Elevation Max M: | 191 |
| Area Km2: | 7.52 |
Longaulnay is a commune in the Ille-et-Vilaine department of Brittany in northwestern France.
Inhabitants of Longaulnay are called in French longaulnéens.