The term ‘object’ in the depth-psychology corpus carries a remarkably diverse semantic load, ranging from the technical object-relations vocabulary of Klein, Winnicott, and their successors to Jung’s epistemological distinction between subject and object as the fundamental polarity of psychic life. For Klein, the ‘object’—originally the breast—is the first target of the infant’s libidinal and destructive impulses; its splitting into good and bad objects, and the ego’s parallel splitting, constitute the foundational drama of inner life. Winnicott refines this framework decisively: the crucial developmental achievement is not merely relating to an object but using one—a shift that demands the object survive the subject’s destruction and thereby establish its independent, external existence. Jung approaches the subject-object axis epistemologically, treating the unconscious projection of psychic contents onto objects as the primitive condition from which consciousness differentiates itself, with each advance in self-awareness constituting a further withdrawal of projection. Lacan reframes the question through the lens of desire and the Other, where the beloved is simultaneously subject and object of desire, while Kohut’s self-psychology displaces classical object language toward ‘selfobjects’—functions rather than things. Across these traditions, the object marks the boundary between self and world, inner and outer, and the history of its theoretical elaboration is inseparable from depth psychology’s central concerns: projection, introjection, transference, and individuation.