Within the depth-psychology corpus, Unio Oppositorum — the union of opposites — stands as one of the most architecturally central concepts in Jungian thought, functioning simultaneously as a psychological telos, an alchemical symbol, and a metaphysical claim about the structure of psychic reality. Jung developed the concept most systematically in Mysterium Coniunctionis (1955), where the alchemical coniunctio serves as the operative image: the union of Sol and Luna, sulphur and mercury, king and queen, figures the psychic work of reconciling conscious and unconscious, masculine and feminine, spirit and matter. The term coniunctio oppositorum appears alongside complexio oppositorum and coincidentia oppositorum as overlapping but technically distinct formulations, each stressing a different aspect of the same fundamental dynamic. Edinger, in the Mysterium Lectures, reads the three stages of coniunctio as the structural epitome of individuation. Von Franz, working through Aurora Consurgens, foregrounds the moral and cosmic register — the union is not merely psychological but soteriological. Hillman approaches the unio mentalis as a prior, more refined stage of the opus, distinct from final union with body and world. Giegerich, characteristically, challenges whether any imaginal or symbolic ‘union’ can substitute for genuine dialectical sublation. The tension between symbolic reconciliation and logical transformation marks the living fault-line in the corpus.