Skip to main content - Ordóñez, José (?–1819)
- Oré, Luis Gerónimo de (c. 1554–1630)
- Oreamuno, Yolanda (1916–1956)
- Orejón y Aparicio, José de (1706–c. 1765)
- Orejones
- Orellana, Francisco De (c. 1511–1546)
- Orellana, José María (1872–1926)
- Oresme, Nicole (c. 1320–1382)
- Orfila, Alejandro (1894–1958)
- Orfila, Washington Alejandro José Luis (1925–)
- Organisation Armée Secrète (OAS)
- Organisation Marocaine Des Droits de l'homme
- Organismic Biology
- Organization for the Liberation of the Occupied South
- Organization of American States (OAS)
- Organization of Arab Petroleum Exporting Countries (OAPEC)
- Organization of Central American States (ODECA)
- Organization of the Islamic Conference
- Oribe, Emilio (?–1975)
- Oribe, Manuel (1792–1857)