| Montigny-l'Allier | |
| Commune Status: | Commune |
| Arrondissement: | Château-Thierry |
| Canton: | Villers-Cotterêts |
| Insee: | 02512 |
| Postal Code: | 02810 |
| Mayor: | Philippe Hennion[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | CA Région de Château-Thierry |
| Coordinates: | 49.1122°N 3.1039°W |
| Elevation Min M: | 55 |
| Elevation Max M: | 151 |
| Area Km2: | 10.14 |
Montigny-l'Allier (pronounced as /fr/) is a commune in the Aisne department in Hauts-de-France in northern France.