Pyrococcus woesei is an ultra-thermophilic marine archaeon. It is sulfur-reducing and grows optimally between 100 and 103 °C. Its cells have a roughly spherical, elongated and constricted appearance, similar to Thermococcus celer. Frequently, they occur as . Cells grown on solid supports have dense tufts of flagella or pili attached to one pole. Kanoksilapatham et al. propose P. woesei as a subspecies of P. furiosus. It is named after the discoverer of archaea as a whole - Carl Woese