During 2000-2001, soil Pythium species were studied in Fars province. Soil samples were collected from various parts of the province (Abadeh, Bajgah, Bayza, Borazjan, Darab, Estahban, Fasa, Khafr, Sepidan, Shiraz, Moharloo, and Zarghan). Isolates were recovered from soil by baiting. Species were identified based on morphological characters of sexual and asexual organs, growth rate at different temperatures, and colony morphology on various media. From 270 isolates of Pythium recovered, 12 species and two groups were identified as: P. aphanidermatum*, P. aquatile, P. deliense, P. diclinum, P. echinulatum, P. inflatum, P. okanoganense, P. oliganderum, P. orthogonon, P. ostracodes, P. rostratum, P. vexans, Pythium Group “G”*, and Pythium Group “HS”* (species with asterisk were predominant). P. aquatile, P. diclinum, P. echinulatum, P. inflatum, P. okanoganense, P. oliganderum, P. orthogonon, P. ostracodes, P. rostratum, and P. vexans are new for Fars, and P. aquatile, P. echinulatum, P. inflatum, P. okanoganense, P. orthogonon, P. ostracodes, and P. rostratum are new for Iran flora.A key is also presented for identification of Fars Pythium species.