| Code | Name | Region |
|---|---|---|
| CAOGO | Osgoode | ON |
| CAOSH | Oshawa | ON |
| CAOSL | Osler | SK |
| CAOYS | Osoyoos | BC |
| CAOTT | Ottawa | ON |
| CAYOW | Ottawa Apt | ON |
| CAOTB | Otterburne | MB |
| CAOTV | Otterville | ON |
| CAOOK | Outlook | SK |
| CAOTM | Outremont | QC |
| CAOWS | Owen Sound | ON |
| CAOXB | Oxbow | SK |
| CAOXF | Oxford | NS |
| CAOSG | Oil Springs | ON |
| CAOKA | Oka | QC |
| CAOFL | Okanagan Falls | BC |
| CAOTS | Okotoks | AB |
| CAYOC | Old Crow | YT |
| CAZFB | Old Fort Bay | QC |
| CAOPL | Old Perlican | NL |
| CAOCA | Oldcastle | ON |
| CAODS | Olds | AB |
| CAOLE | O'leary | PE |
| CAOVR | Oliver | BC |
| CAOMM | Omemee | ON |
| CAOPH | Ompah | ON |
| CAONP | Onaping | ON |
| CAOLL | Onion Lake | SK |
| CAOWY | Onoway | AB |
| CAS8W | Onslow | NS |
| CAOGD | Orangedale | NS |
| CAORA | Orangeville | ON |
| CAORF | Orford | QC |
| CANDL | Notre-dame-de-lourdes | MB |
| CANDS | Notre-dame-des-pins | QC |
| CANPS | Notre-dame-des-prairies | QC |
| CANBC | Notre-dame-du-bon-conseil | QC |
| CANND | Notre-dame-du-mont-carmel | QC |
| CANUD | Notre-dame-du-nord | ON |
| CANTW | Nottawa | ON |
| CANYN | Noyan | QC |
| CANTY | Nuttby | NS |
| CAOBY | Oak Bay | BC |
| CAKRV | Oak Bluff | MB |
| CAOAL | Oak Lake | MB |
| CAOBK | Oakbank | MB |
| CAOAJ | Oakville | MB |
| CAOAK | Oakville | ON |
| CAYDW | Obre Lake | NT |
| CAOFA | Ocean Falls | BC |