- Oberholzer, Emil (1883-1958)
- Object
- Object A
- Object Relations Theory
- Object, Change of/Choice of
- Obsession
- Obsessional Neurosis
- Occultism
- Oceanic Feeling
- Odier, Charles (1886-1954)
- Oedipus Complex
- Oedipus Complex, Early
- Omnipotence of Thoughts
- On Dreams
- On Narcissism: An Introduction
- On the History of the Psychoanalytic Movement
- On the Origin of the 'Influencing Machine' in Schizophrenia
- On the Sexual Theories of Children
- On Transience
- Ontogenesis
- Operational Thinking
- Opere (Writings of Sigmund Freud)
- Ophuijsen, Johan H. W. van (1882-1950)
- Optical Schema
- Oral Stage
- Oral-Sadistic Stage
- Orality
- Organ Pleasure
- Organic Psychoses
- Organic Repression
