Phthinosuchia is an extinct group of therapsids including two poorly known species, Phthinosuchus discors and Phthinosaurus borrisiaki, from the Middle Permian of Russia.

Phthinthosuchus is known a partial crushed skull and Phthinosaurus is known from an isolated lower jaw.

[1] The two species have traditionally been grouped together based on their shared primitive characteristics, but more recent studies have proposed that they are more distantly related.

[4] Phthinosuchia was named by American paleontologist Everett C. Olson in 1961, who considered it the most primitive infraorder within Therapsida.

A year later Olson named the new infraorder Eotheriodontia and reclassified Phthinosuchia as a subgroup of eotheriodonts, along with the families Biarmosuchidae and Brithopodidae.