Identity diffusion is one of the defining characteristics of borderline personality disorder (BPD). Given its central importance in the formal diagnostic criteria for personality disorders, identity diffusion is remarkably under-researched. In particular, our knowledge of the phenomenology of identity diffusion needs to be improved. This study is based on semistructured interviews with 16 younger women SCID-5-diagnosed with BPD. All interviews were analyzed using the interpretative phenomenological analysis approach. On the basis of this analysis, the patients' descriptions of how identity diffusion manifests itself in their subjective experience are classified into nine categories: disintegrated self-image; using various façades to stabilize the self; painful feelings of the self as broken; feeling that the self does not fit in; inner emptiness; “I don't know what I want”; great need for attention from others to stabilize identity; feeling unable to handle interpersonal relationships; and using sex to distract the self and regulate painful self-states.