| Code | Name | Region |
|---|---|---|
| NLOMH | Oostmahorn | FR |
| NLOST | Oostrum | FR |
| NLOTR | Oostrum | LI |
| NLOSO | Oost-souburg | ZE |
| NLOOL | Ooststellingwerf | GE |
| NLOVN | Oostvoorne | |
| NLOWI | Oldambt | OV |
| NLOLD | Oldeberkoop | |
| NLOLB | Oldebroek | GE |
| NLODD | Oldeholtpade | FR |
| NLOLE | Oldehove | GR |
| NLOLK | Oldemarkt | |
| NLOLZ | Oldenzaal | |
| NLOWE | Oldeouwer | FL |
| NLOSI | Olst | OV |
| NLOBK | Olst-wijhe | LI |
| NLOML | Ommel | NB |
| NLOMM | Ommen | |
| NLORE | Ommeren | GE |
| NLOOW | Onderbanken | FR |
| NLOOY | Ooij | |
| NLOGP | Ooltgensplaat | ZH |
| NLOPT | Oost Gelre | FR |
| NLOBG | Oostburg | ZE |
| NLOSD | Oostdijk | |
| NLOOE | Oosteind | NB |
| NLNNN | Nuenen | |
| NLNGN | Nuenen | NB |
| NLNUI | Nuis | |
| NLNUL | Nuland | NB |
| NLNUD | Numansdorp | |
| NLNNM | Nunhem | LI |
| NLNUN | Nunspeet | |
| NLNTH | Nuth | |
| NLOBD | Obdam | |
| NLOCC | Ochten | |
| NLODK | Odijk | |
| NLODL | Odiliapeel | NB |
| NLODN | Odoorn | |
| NLOGE | Oegstgeest | |
| NLOGW | Offingawier | FR |
| NLOEL | Ohe En Laak | LI |
| NLOIL | Oirlo | LI |
| NLOIH | Oirschot | |
| NLOIW | Oisterwijk | |
| NLOBE | Olburgen | GE |
| NLNGD | Nooit Gedacht | DR |
| NLNMT | Noordbeemster | NH |
| NLOOG | Noordbergum | FR |
| NLNOQ | Noord-beveland | ZE |