word | | Country name |
| oloto | Samoa | conventional long form: Independent State of Samoa conventional short form: Samoa local long form: Malo Sa'oloto Tuto'atasi o Samoa local short form: Samoa former: Western Samoa |
| Oman | Oman | conventional long form: Sultanate of Oman conventional short form: Oman local long form: Saltanat Uman local short form: Uman former: Muscat and Oman |
| Oman | United Arab Emirates | conventional long form: United Arab Emirates conventional short form: none local long form: Al Imarat al Arabiyah al Muttahidah local short form: none former: Trucial Oman, Trucial States abbreviation: UAE |
| Oriental | Uruguay | conventional long form: Oriental Republic of Uruguay conventional short form: Uruguay local long form: Republica Oriental del Uruguay local short form: Uruguay former: Banda Oriental, Cisplatine Province |
| Oro | Western Sahara | conventional long form: none conventional short form: Western Sahara former: Rio de Oro, Saguia el Hamra, Spanish Sahara |
| Outer | Mongolia | conventional long form: none conventional short form: Mongolia local long form: none local short form: Mongol Uls former: Outer Mongolia |
| outre | French Polynesia | ... form: Overseas Lands of French Polynesia conventional short form: French Polynesia local long form: Pays d'outre-mer de la Polynesie Francaise local short form: Polynesie Francaise former: French Colony of Oceania |
| outre | Saint Barthelemy | conventional long form: Overseas Collectivity of Saint Barthelemy conventional short form: Saint Barthelemy local long form: Collectivite d'outre mer de Saint-Barthelemy local short form: Saint-Barthelemy |
| outre | Saint Martin | conventional long form: Overseas Collectivity of Saint Martin conventional short form: Saint Martin local long form: Collectivity d'outre mer de Saint-Martin local short form: Saint-Martin |
| Overseas | French Polynesia | conventional long form: Overseas Lands of French Polynesia conventional short form: French Polynesia local long form: Pays d'outre-mer de la Polynesie Francaise local short form: Polynesie Francaise former: French Colony ... |
| Overseas | Saint Barthelemy | conventional long form: Overseas Collectivity of Saint Barthelemy conventional short form: Saint Barthelemy local long form: Collectivite d'outre mer de Saint-Barthelemy local short form: Saint-Barthelemy |