| Ville de regroupement | Ville | C.Pos | Langue |
| PONT-A-CELLES | OBAIX | 6230 | F |
| PECQ | OBIGIES | 7743 | F |
| MONS | OBOURG | 7034 | F |
| LIBIN | OCHAMPS | 6890 | F |
| CLAVIER | OCQUIER | 4560 | F |
| MANHAY | ODEIGNE | 6960 | F |
| CRISNEE | ODEUR | 4367 | F |
| BEERNEM | OEDELEM | 8730 | N |
| ROESELARE | OEKENE | 8800 | N |
| RANST | OELEGEM | 2520 | N |
| ALVERINGEM | OEREN | 8690 | N |
| DENTERGEM | OESELGEM | 8720 | N |
| GOOIK | OETINGEN | 1755 | N |
| FRASNES-LEZ-ANVAING | OEUDEGHIEN | 7911 | F |
| WESTERLO | OEVEL | 2260 | N |
| PALISEUL | OFFAGNE | 6850 | F |
| LESSINES | OGY | 7862 | F |
| LASNE | OHAIN | 1380 | F |
| OHEY | OHEY | 5350 | F |
| VIROINVAL | OIGNIES-EN-THIERACHE | 5670 | F |
| TUBIZE | OISQUERCQ | 1480 | F |
| BIEVRE | OIZY | 5555 | F |
| NINOVE | OKEGEM | 9400 | N |
| OLEN | OLEN | 2250 | N |
| WAREMME | OLEYE | 4300 | F |
| LESSINES | OLLIGNIES | 7866 | F |
| VIROINVAL | OLLOY-SUR-VIROIN | 5670 | F |
| BALEN | OLMEN | 2491 | N |
| OLNE | OLNE | 4877 | F |
| ZULTE | OLSENE | 9870 | N |
| GEER | OMAL | 4252 | F |
| AMAY | OMBRET | 4540 | F |
| PHILIPPEVILLE | OMEZEE | 5600 | F |
| MARCHE-EN-FAMENNE | ON | 6900 | F |
| ONHAYE | ONHAYE | 5520 | F |
| ONHAYE | ONHAYE | 5523 | F |
| GERAARDSBERGEN | ONKERZELE | 9500 | N |
| HONNELLES | ONNEZIES | 7387 | F |
| JEMEPPE-SUR-SAMBRE | ONOZ | 5190 | F |
| ROOSDAAL | ONZE-LIEVE-VROUW-LOMBEEK | 1760 | N |
| SINT-KATELIJNE-WAVER | ONZE-LIEVE-VROUW-WAVER | 2861 | N |
| WIELSBEKE | OOIGEM | 8710 | N |
| OUDENAARDE | OOIKE | 9700 | N |
| WORTEGEM-PETEGEM | OOIKE | 9790 | N |
| SINT-LIEVENS-HOUTEM | OOMBERGEN | 9520 | N |
| ZOTTEGEM | OOMBERGEN | 9620 | N |
| TIENEN | OORBEEK | 3300 | N |
| LEDE | OORDEGEM | 9340 | N |
| GENT | OOSTAKKER | 9041 | N |
| GENT | OOSTAKKER | 9042 | N |
| KOKSIJDE | OOSTDUINKERKE | 8670 | N |
| ASSENEDE | OOSTEEKLO | 9968 | N |
| OOSTENDE | OOSTENDE | 8400 | N |
| OOSTERZELE | OOSTERZELE | 9860 | N |
| HAM | OOSTHAM | 3945 | N |
| OOSTKAMP | OOSTKAMP | 8020 | N |
| DAMME | OOSTKERKE | 8340 | N |
| DIKSMUIDE | OOSTKERKE | 8600 | N |
| MALLE | OOSTMALLE | 2390 | N |
| STADEN | OOSTNIEUWKERKE | 8840 | N |
| OOSTROZEBEKE | OOSTROZEBEKE | 8780 | N |
| VLETEREN | OOSTVLETEREN | 8640 | N |
| ZOMERGEM | OOSTWINKEL | 9931 | N |
| BRAKEL | OPBRAKEL | 9660 | N |
| BUGGENHOUT | OPDORP | 9255 | N |
| OPGLABBEEK | OPGLABBEEK | 3660 | N |
| MAASMECHELEN | OPGRIMBIE | 3630 | N |
| BRAINE-L'ALLEUD | OPHAIN-BOIS-SEIGNEUR-ISAAC | 1421 | F |
| GERAARDSBERGEN | OPHASSELT | 9500 | N |
| HEERS | OPHEERS | 3870 | N |
| HELECINE | OPHEYLISSEM | 1357 | F |
| KINROOI | OPHOVEN | 3640 | N |
| BREE | OPITTER | 3960 | N |
| TIENEN | OPLINTER | 3300 | N |
| MAASEIK | OPOETEREN | 3680 | N |
| PALISEUL | OPONT | 6852 | F |
| INCOURT | OPPREBAIS | 1315 | F |
| SINT-AMANDS | OPPUURS | 2890 | N |
| BIERBEEK | OPVELP | 3360 | N |
| OPWIJK | OPWIJK | 1745 | N |
| PERWEZ | ORBAIS | 1360 | F |
| VRESSE-SUR-SEMOIS | ORCHIMONT | 5550 | F |
| TOURNAI | ORCQ | 7501 | F |
| SINT-TRUIDEN | ORDINGEN | 3800 | N |
| METTET | ORET | 5640 | F |
| OREYE | OREYE | 4360 | F |
| BERTRIX | ORGEO | 6880 | F |
| ATH | ORMEIGNIES | 7802 | F |
| ORP-JAUCHE | ORP-JAUCHE | 1350 | F |
| ORP-JAUCHE | ORP-LE-GRAND | 1350 | F |
| MONT-DE-L'ENCLUS | ORROIR | 7750 | F |
| LINTER | ORSMAAL-GUSSENHOVEN | 3350 | N |
| LA ROCHE-EN-ARDENNE | ORTHO | 6983 | F |
| ATH | OSTICHES | 7804 | F |
| ZWEVEGEM | OTEGEM | 8553 | N |
| BURDINNE | OTEPPE | 4210 | F |
| AWANS | OTHEE | 4340 | F |
| OREYE | OTRANGE | 4360 | F |
| HULDENBERG | OTTENBURG | 3040 | N |
| ERPE-MERE | OTTERGEM | 9420 | N |
| OTTIGNIES-LOUVAIN-LA-NEUVE | OTTIGNIES | 1340 | F |
| OTTIGNIES-LOUVAIN-LA-NEUVE | OTTIGNIES-LOUVAIN-LA-NEUVE | 1340 | F |
| DENDERMONDE | OUDEGEM | 9200 | N |
| DIKSMUIDE | OUDEKAPELLE | 8600 | N |
| OUDENAARDE | OUDENAARDE | 9700 | N |
| SINT-PIETERS-LEEUW | OUDENAKEN | 1600 | N |
| OUDENBURG | OUDENBURG | 8460 | N |
| BRUSSEL | OUDERGEM | 1160 | N |
| OUD-HEVERLEE | OUD-HEVERLEE | 3050 | N |
| OUD-TURNHOUT | OUD-TURNHOUT | 2360 | N |
| OUFFET | OUFFET | 4590 | F |
| LIEGE | OUGREE | 4000 | F |
| SERAING | OUGREE | 4102 | F |
| OUPEYE | OUPEYE | 4680 | F |
| OUPEYE | OUPEYE | 4682 | F |
| NINOVE | OUTER | 9406 | N |
| HOEGAARDEN | OUTGAARDEN | 3321 | N |
| MODAVE | OUTRELOUXHE | 4577 | F |
| AVELGEM | OUTRIJVE | 8582 | N |
| ZINGEM | OUWEGEM | 9750 | N |
| GERAARDSBERGEN | OVERBOELARE | 9500 | N |
| LINTER | OVERHESPEN | 3350 | N |
| OVERIJSE | OVERIJSE | 3090 | N |
| BERLARE | OVERMERE | 9290 | N |
| OVERPELT | OVERPELT | 3900 | N |
| TONGEREN | OVERREPEN | 3700 | N |
| LANDEN | OVERWINDEN | 3400 | N |
