Oaxaca, Mexico Obalno-kraška, Slovenia Oberösterreich, Austria Obock, Djibouti Obwalden, Switzerland Occidental Mindoro, Philippines Ocniţa, Moldova Ocotepeque, Honduras Odessa, Ukraine Odisha, India Ogooué-Ivindo, Gabon Ogooué-Lolo, Gabon Ogooué-Maritime, Gabon Ogun, Nigeria Ohangwena, Namibia Ohio, United States Ohrid, Macedonia Oio, Guinea-Bissau Oita, Japan Okayama, Japan Okinawa, Japan Oklahoma, United States Olancho, Honduras Olomoucký, Czech Republic Olt, Romania Omaheke, Namibia Ombella-M'Poko, Central African Republic Omsk, Russia Omusati, Namibia Ondo, Nigeria Ontario, Canada Opole, Poland Oppland, Norway Oran, Algeria Orange Walk, Belize Ordino, Andorra Ordu, Turkey Orebro, Sweden Oregon, United States Orel, Russia Orellana, Ecuador Orenburg, Russia Orhei, Moldova Orhon, Mongolia Oriental, Morocco Oriental Mindoro, Philippines Orientale, Democratic Republic of the Congo Oro, Papua New Guinea Oromia, Ethiopia Oruro, Bolivia