| One for all, All for one | | Country |
| Ongoing Bribery Investigations | | Country |
| Ongoing Industrial Relocation | | Country |
| Ongoing Rearmament | | Country |
| Opel | | Materiel Manufacturer |
| Opel Abt. Rumänien | | Materiel Manufacturer |
| Operación Ocaso Escarlata | | Country |
| Operation AN | | Country |
| Operation Bolivar | | Country |
| Operation: Save Denmark | | Country |
| Operation: Save Norway | | Country |
| Operational Reserves | | Division Command Spirit |
| Opium Trade | | Country |
| Oppose the Communists | | Country |
| Oppressed Working Class | | Country |
| Optimization of the Production Lines | | Country |
| Order and Progress | | Country |
| Ordered Partition | | Country |
| Ordnance Bureau | | Materiel Manufacturer |
| Ordnance Factories Board | | Materiel Manufacturer |
| Organization of African Unity Member | | Country |
| Organization of American States Member | | Country |
| Organization Todt | | Industrial Concern |
| Oriental Development Company | | Industrial Concern |
| Orthodox Church Support | | Country |
| Osaka Army Arsenal | | Tank Manufacturer |
| Ossewabrandwag | | Country |
| Ossewabrandwag | | Country |
| Ossewabrandwag | | Country |
| ÖSterreichische Fleugzeugfabrik | | Aircraft Manufacturer |
| ÖSterreichische Sauerwerke | | Materiel Manufacturer |
| Ostwall Construction | | Country |
| Our Economic Miracle | | Country |
| Our Fighting Spirit | | Country |
| Our Finest | | Country |
| Our nation Currency Board | | Country |
| Our nation Research Collaboration | | Country |
| Our Solidarity | | Country |
| Our State Railways | | Industrial Concern |
| Our Volunteer Force | | Country |
| Our Volunteer Forces | | Country |
| Outokumpu | | Industrial Concern |
| Outsourced Weapons Production | | Country |
| Overwhelming Firepower | | Army Spirit |
| Pacific Currency Union Member | | Country |
| Pact of Steel | | Country |
| Paldiski Port | | Naval Manufacturer |
| Pan-Arabism Crackdown | | Country |
| Pan-Hispanic Rhetoric | | Country |
| Pan-Hispanic Rhetoric | | Country |
