- New Spain. Viceroy1
- Odyssey (Homer)1
- Ontology1
- Order of the Golden Fleece1
- Ordinances, Municipal1
- Otto I, Holy Roman Emperor, 912-9731
- Ovando, Nicolás de, approximately 1460-15111
- Oviedo family1
- Oviedo, Francisco de, 1728-1
- Oviedo, Gregorio de, 1721-17961
- Oviedo, Nicolás de, 1725-1
- Panama--Panama1
- Papacy1
- Papal documents1
- Perez Barahona, Juan, active 1560-15621
- Peru (Viceroyalty). Real Caja de Cuzco1
- Peru--Lima1
- Philip III, King of Spain, 1578-16211
- Philip IV, King of Spain, 1605-16651
- Philippines1