| City | Country |
|---|---|
| Oroquieta | Philippines |
| Ouezzane | Morocco |
| Osakasayama | Japan |
| Oyem | Gabon |
| Ohrid | Macedonia |
| Ocosingo | Mexico |
| Odienne | Côte d'Ivoire |
| Ostersund | Sweden |
| Oizumi | Japan |
| Or Yehuda | Israel |
| Oshakati | Namibia |
| Oltenita | Romania |
| Oharu | Japan |
| Ometepec | Mexico |
| Ocotal | Nicaragua |
| Oullins | France |
| Otjiwarongo | Namibia |
| Olgiy | Mongolia |
| Oegstgeest | Netherlands |
| Ocatlan | Mexico |
| Ouesso | Congo (Brazzaville) |
| Orly | France |
| Oulad Tayeb | Morocco |
| Oji | Japan |
| Oadby | United Kingdom |
| Oxkutzkab | Mexico |
| Onex | Switzerland |
| Ottobrunn | Germany |
| Ojinaga | Mexico |
| Owando | Congo (Brazzaville) |
| Opfikon | Switzerland |
| Ogre | Latvia |
| Oulad Fraj | Morocco |
| Obock | Djibouti |
| Orhei | Moldova |
| Ostermundigen | Switzerland |
| Oteapan | Mexico |
| Oyamazaki | Japan |
| Orange Walk | Belize |
| Ovenden | United Kingdom |
| Oulad Hamdane | Morocco |
| Ogijares | Spain |
| Ozurgeti | Georgia |
| Oulad Ayyad | Morocco |
| Ondorhaan | Mongolia |
| Oakham | United Kingdom |
| Ormesson-sur-Marne | France |
| Obo | Central African Republic |
| Oulad Ben Sebbah | Morocco |
| Oban | United Kingdom |