Urine occupies a surprisingly rich and multi-layered position within the depth-psychology corpus, appearing across three largely distinct but occasionally overlapping registers: alchemical-symbolic, psychoanalytic-developmental, and clinical-diagnostic. In the alchemical tradition as interpreted by Hillman and Abraham (Lyndy), urine figures as a primary materia — specifically the ‘urine of a virgin boy,’ identified with the materia prima and the mercurial lumen naturalis. Hillman’s reading of the 1669 discovery of phosphorus from cooked urine literalizes the alchemical dictum urina puerorum est mercurius, locating in this substance the very principle of light-bearing interiority. For Karl Abraham, working squarely within Freudian developmental theory, urine functions as a vehicle of urethral erotism, narcissistic omnipotence, and infantile ambivalence — appearing in premature ejaculation, the female castration complex, and the aggressive ‘soiling’ of the love-object. Bleuler documents urine’s anomalies — polyuria, retention, glycosuria — as somatic indices of schizophrenic dysregulation. In contemporary clinical research, urine testing operates as a straightforward biomarker for substance use monitoring. The term thus traverses the full arc from archaic symbol to clinical instrument, making it an unusually productive site for understanding how depth psychology negotiates body, image, and matter.