Persistent sciatic artery (PSA) is an exceptionally rare congenital vascular anomaly with profound clinical implications. This condition occurs when the primitive sciatic artery, responsible for fetal lower limb blood supply, fails to regress during embryonic development. PSA persists into adulthood, representing an intriguing vascular variation that can present as gluteal aneurism and thrombosis. We present the case of a 72-year-old female patient admitted with abdominal pain and blackening of her right foot. Clinical examination revealed dry gangrene affecting the toes, limb edema, and absent peripheral pulses in the right lower limb. Septic shock and electrolyte imbalances prompted immediate resuscitation and antibiotic therapy. Diagnostic investigations, including Doppler ultrasonography, CT angiography, and 2D echocardiography, identified a right-sided PSA. With limb ischemia being irreversible, a below-knee amputation was performed. This case highlights the clinical presentation, diagnostic workup, and management of a rare PSA, emphasizing the importance of prompt recognition and intervention in complex vascular anomalies.