| Obaix-Buzet | FXB |  |
| Obigies | FII | |
| Obourg | LRG | |
| Offange | MOG | |
| Ogy | OGY | |
| Oisquercq | FOT | |
| Okegem | FKO | |
| Olen | GOL | |
| Olen | GOO | |
| Ollignies | LOG | |
| Olloy-sur-Viroin | LOY | |
| Olsene | FSO | |
| Ondenvalle | |
|
| Onoz-Spy | LNZ | |
| oostakker | FOA | |
| Oostende | FSD | |
| Oostende-Kaai | FSDQ | |
| Oostham | LOM | |
| Oostkamp | FPO | |
| Oostkerke | FOT | |
| Oostrozebeke | FOK | |
| Opbrakel | |
|
| Oplinter | LIE | |
| Opoeteren-Dilsen | FO | |
| Oppuurs | LPU | |
| Opwijk | FKW | |
| Ordingen | FOD | |
| Oret | LRT | |
| Orgéo | |
|
| Orgéo-Ardoisières | |
|
| Orgéo-Gribomont | GEO | |
| Ormeignies | LGM | |
| Orp | ORP | |
| Orroir | FOR | |
| Ottignies | LT | |
| Oud-Heverlee | GVH | |
| Oudeburg | FUDS | |
| Oudegem | FDM | |
| Oudenaarde | FDN | |
| Oudergem-Station | MDM | |
| Oudergem-Waversesteenweg | |
|
| Oudler | |
|
| Ougree | LGR | |
| Ourt | |
|
| Overboelare | |
|
| Overpelt | GOV | |
| Overpelt-Dorp | |
|
| Overpelt-Werkplaatsen | GOU | |