Unconscious phantasy occupies a contested but generative position across the depth-psychology corpus. In the Kleinian tradition it designates the primary psychic content from the outset of life: every impulse, anxiety, and defence is held to have a corresponding phantasy, an unconscious mental representation through which the infant apprehends and acts upon internal and external reality. Klein’s own writings foreground the interpenetration of phantasy and actual experience in the infant’s world, insisting that transference analysis must reach the ‘phantastic’ distortions wrought by projection and idealization. Bion extends this framework by linking phantasy to the very processes of toleration and modification of frustration. For Freud, unconscious phantasy occupies the crucial intermediate position between wishful impulse and symptom formation: phantasies, once preconscious, may be repressed and become the sites to which libido retreats, generating neurotic organisation. In the Jungian field, the concept runs under different names — ‘unconscious fantasy,’ ‘fantasy-thinking,’ and ultimately active imagination — yet the structural question is analogous: how do imaginal products emanating from below the threshold of consciousness relate to the ego and to archetypal structures? Samuels explicitly identifies Klein’s unconscious fantasy as the psychoanalytic idea most nearly aligned with Jung’s archetypal theory, while also noting the distinction’s clinical importance. Lacan, characteristically, formalises phantasy as a structure ($◇a), repositioning it within a theory of desire rather than developmental experience.