| Ly-Fontaine | |
| Commune Status: | Commune |
| Arrondissement: | Saint-Quentin |
| Canton: | Ribemont |
| Insee: | 02446 |
| Postal Code: | 02440 |
| Mayor: | Jérôme Vasseur[1] |
| Term: | 2020 - 2026 |
| Coordinates: | 49.7353°N 3.3086°W |
| Elevation M: | 90 |
| Elevation Min M: | 65 |
| Elevation Max M: | 100 |
| Area Km2: | 3.47 |
Ly-Fontaine (in French pronounced as /lifɔ̃tɛn/) is a commune in the Aisne department in Hauts-de-France in northern France.