- Government, Origin of
- Oath, The (Hippocrates)
- Objections Against the Meditations and Replies
- Obscure, Jude the
- Observation and Experiment
- Observations on "Wild" Psychoanalysis
- Odes (Horace)
- Odes, Isthmian
- Odes, Nemean
- Odes, Olympian
- Odes, Pythian
- Odyssey
- Oedipus at Colonus
- Oedipus the King
- Old Age, On
- Old Age, On Life and Death, On Breathing; On Youth and
- Old Man and the Sea, The
- Oliver Twist
- Olympian Odes
- One Day in the Life of Ivan Denisovich
- One Hundred Years of Solitude
- One Thousand and One Arabian Nights
- One's Own, A Room of
- Opticks
- Orations (Cicero)
- Oratory, Dialogue on
- Orchard, The Cherry
- Oresteia, The (Aeschylus)
- Orestes (Euripides)
- Organon
- Organum, Novum
- Origin and Development of the Quantum Theory
- Origin and Development of Psychoanalysis, The
- Origin of Government
- Origin of Inequality, On the
- Origin of Species, The
- Original Contract, Of the
- Orlando Furioso
- Othello, Moor of Venice
- Outline of History, The
- Outpost of Progress, An
- Overcoat, The
- Oz, The Wonderful Wizard of
- Ozymandias
