- Obstetrics1
- Occasional poems1
- Orden de Santiago1
- Order of the Garter1
- Order of the Golden Fleece1
- Orders of knighthood and chivalry1
- Ordinances, Municipal1
- Orta, Garcia de, active 16th century1
- Ospedale degli Innocenti (Florence, Italy)1
- Ospedale di San Bartolomeo (Florence, Italy)2
- Ovando, Nicolás de, approximately 1460-15111
- Paganelli, Roberto1
- Pain--Religious aspects--Christianity1
- Painted bindings1
- Painting7
- Pakistan--Wazīrābād1
- Panama--Panama1
- Pandnāmah (ʻAṭṭār, Farīd al-Dīn)1
- Paolo, Stefano di1
- Papacy2