The current case presents a patient who was admitted to our hospital with the diagnosis of cellulitis of the right groin. In the following days, the patient's condition deteriorated and developed a septic shock. Exploration in the operating room showed a necrotising fasciitis of the adductor muscles, with an infected sebaceous cyst in the inguinal crest as port d'entrée. After extensive surgical debridement, antibiotic therapy, haemodynamic and respiratory support, the patient recovered. Necrotising fasciitis is a rare but very lethal condition, which necessitates aggressive surgical therapy and antibiotic support. The current case report is the first report to show a necrotising fasciitis due to an infected sebaceous cyst.