Author
- Nicolaus von Grätz1
- Nicoluccio di Ascoli1
- Nicolò Peranzone1
- Nilus of Sinai1
- Oddo di Biagio1
- Oliver Maillard1
- Order of the Immaculate Conception1
- Orderic Vitalis1
- Orosius1
- Osbern of Gloucester1
- Oswald Corda1
- Ottmar Luscinius1
- Papias1
- Parliament of Great Britain1
- Paul III1
- Paul IV1
- Paul of Pergula1
- Paul of Venice1
- Paul the Deacon1
- Paul, of Cologne1