| Fontaine-sous-Montdidier | |
| Commune Status: | Commune |
| Arrondissement: | Montdidier |
| Canton: | Roye |
| Insee: | 80326 |
| Postal Code: | 80500 |
| Mayor: | Dominique Fievez[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | CC Grand Roye |
| Coordinates: | 49.6575°N 2.5194°W |
| Elevation M: | 100 |
| Elevation Min M: | 46 |
| Elevation Max M: | 127 |
| Area Km2: | 9.03 |
Fontaine-sous-Montdidier (in French pronounced as /fɔ̃tɛn su mɔ̃didje/, literally Fontaine under Montdidier; Picard: Fontainne-dsou-Montdidji) is a commune in the Somme department in Hauts-de-France in northern France.
The commune is situated on the D26 road, 40km (30miles) southeast of Amiens.