Obsession occupies a cardinal position in the depth-psychology corpus, functioning simultaneously as a clinical diagnosis, a phenomenological description of psychic captivity, and a symbol of the unconscious asserting its authority over the ego. Freud’s foundational architecture treats obsessional neurosis as a discrete nosological entity — distinguished from hysteria by its internalized, non-somatic character — grounded in libidinal regression to the sadistic-anal organization, where loving impulses are masked as murderous ones. Abraham extends this framework by charting the structural affinities between obsessional neurosis and melancholia, tracing both to ambivalence, libidinal fixation, and the chronic tension between love and hate. Winnicott reframes the obsessional ritual as a failed religious ceremony, a caricature of expiation that cannot dissolve the underlying confusion it seeks to conceal — namely, that hate has overmastered love. Hollis, working in the Jungian idiom, reads obsession as the inevitable consequence of unconscious contents that cannot be owned: what remains unacknowledged becomes compulsive, flooding the ego with unbidden affect. The Twelve-Step tradition, via Kurtz, absorbs and repackages the obsession concept as the mental dimension of addiction, complementing physical allergy with a spiritual pathology of the will. Across all these registers, obsession marks the precise boundary where voluntary agency collapses and autonomous psychic forces take command — making it indispensable for any account of suffering, compulsion, and the possibility of transformation.