Former Owner
- Octave Chavaillor1
- Oliver Henry Perkins2
- Oliver R. Barrett1
- Oric Bates1
- Otto Ege1
- P. Pigeot1
- Paolo Vimercati Sozzi1
- Paul Gottschalk1
- Paul Louis Feiss1
- Paul Riant2
- Peter Arrell Brown Widener2
- Peter Arrell Brown Widener II2
- Peter Ludwig3
- Petrus Jensenius1
- Petrus Leonardus1
- Petrus Martinotius1
- Petrus Ysermans1
- Philip Carteret Webb1
- Philippe de Béthune1
- Phillip J. Pirages Fine Books & Manuscripts1