Probainognathus (Greek: "progressive jaw") is a genus of carnivorous cynodont therapsid that lived during the lower Upper Triassic of South America. This creature had an incipient squamosal-dentary jaw-cranium joint, which is a clearly mammalian anatomical feature. It was at the very least closely related to the family of Chiniquodontidae, in which some authors have included it. Some broadly similar teeth from Europe were described under the name of Lepagia.