- Ospedale degli Innocenti (Florence, Italy)1
- Otto I, Holy Roman Emperor, 912-9731
- Paganelli, Roberto1
- Papal legates1
- Paraphrases1
- Paul V, Pope, 1552-16211
- Pazzi Conspiracy (1478)1
- Penitentials1
- Persephone (Greek deity)1
- Pesciori, Guglielmo1
- Phalaris, Tyrant of Agrigentum, active 6th century B.C.1
- Pharmacognosy1
- Pharmacology1
- Pharmacy1
- Philip II, King of Spain, 1527-15981
- Philip III, King of Spain, 1578-16211
- Piccolomini, Alessandro1
- Piccolomini, Andreas1
- Piccolomini, Antonio Maria d'Enea1
- Piccolomini, Giacomo d'Antonio Maria d'Enea1