In French Guiana, Bothrops atrox, Bothrops brazili, Bothrops bilineatus, Lachesis muta and Micrurus sp are responsible for most cases of snakebite envenomation. The clinical features in patients suffering from envenomations by viperid snakes involve local tissue damage and systemic manifestations, such as hemorrhage, coagulopathies and hemodynamic instability. We report a severe case of envenomation in a patient bitten by a large unidentified pit viper in French Guiana. Due to lack of antivenom, the patient only received symptomatic management. Severe manifestations of local and systemic envenomation developed, and the patient needed multiple debridement procedures and ultimately required a transfemoral amputation. In addition, Aeromonas hydrophila was cultivated from the affected tissue, suggesting that infection contributed to necrotizing fasciitis. This case highlights the clinical features of a severe viperid snakebite envenomation, and illustrates the urgent need to ensure accessibility of effective and safe polyvalent viperid antivenom in French Guiana.