Phaanthosaurus is an extinct genus of basal procolophonid parareptile from early Triassic (Induan stage) deposits of Nizhnii Novgorod, Russian Federation. It is known from the holotype PIN 1025/1, a mandible (a dentary). It was collected from Vetluga River, Spasskoe village and referred to the Vokhmian terrestrial horizon of the Vokhma Formation. It was first named by P. K. Chudinov and B. P. Vjushkov in 1956 and the type species is Phaanthosaurus ignatjevi.