- 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