Fournier's gangrene is a life-threatening fascial infection. We report a case of a 65-year-old diabetic man with a history of obstructive prostate growth who developed ischemic penile gangrene following traumatic transurethral catheterization. Despite initial debridement, progressive necrosis necessitated total penectomy and cystostomy. This case highlights the potential for devastating consequences of failed catheterization and the importance of early urologic intervention.