Ontological vulnerability names the condition in which the very structure of human being — not merely its psychological surface — is constituted by exposure, finitude, and susceptibility to dissolution. Across the depth-psychology corpus, the term operates at the intersection of existential phenomenology, Buddhist-informed psychotherapy, and ethical philosophy. Heidegger’s analytic of Dasein furnishes the foundational grammar: care (Sorge), thrownness, and Being-toward-death collectively disclose a being whose existence is never self-grounding, never invulnerable to the claim of its own finitude. Welwood imports this insight into clinical practice, arguing that the wound is not a defect to be repaired but a threshold through which a more authentic presence becomes available — vulnerability as portal rather than liability. Kurtz locates ontological vulnerability within the A.A. tradition’s ‘shared honesty of mutual vulnerability,’ where the acknowledgment of constitutive weakness is the precondition of genuine community. Nussbaum, working from Greek tragedy and Aristotle, frames the same terrain through the fragility of human excellence: our dependence on relational goods, luck, and embodied circumstance is not a contingent misfortune but the very structure of eudaimonia. The central tension across these voices concerns whether ontological vulnerability is primarily to be accepted (Welwood, Kurtz), philosophically honored (Nussbaum), or existentially appropriated through resoluteness (Heidegger). All agree that its denial generates the most damaging pathologies the psyche can produce.