| OAKLAND,California |
| OAMARU,New Zealand |
| ODESSA,Ukraine |
| OITA,Japan |
| OKINAWA,Japan |
| OMAEZAKI,Japan |
| OMAHA,Nebraska |
| OMSK,Russia |
| ONAHAMA,Japan |
| ONNE,Nigeria |
| ONSAN,South Korea |
| OPORTO,Portugal |
| ORAN,Algeria |
| ORANJESTAD,Aruba |
| ORLANDO,Florida |
| ORLEANS,France |
| OROBAY,Papua New Guinea |
| ORSA,Russia |
| ORZEA,Russia |
| OSAKA,Japan |
| OSH,Kyrgyzstan |
| OSLO,Norway |
| OTALU,Japan |
| OTARU,Japan |
| OXFORD,U.K. |