The robust Australopithecines, sometimes placed in the genus Paranthropus, consisted of three species and emerged as early as 2.6 million years ago. These species resided in East and South Africa until their extinction 1.4 million years ago and are often considered a “side branch” in hominin evolutionary history. The robust features of the skulls of these species have long been assumed to be adaptations for a hard food diet. In this review, the dentition, mandible, maxilla, palate, basicranium, zygomatic arches and foramina, and sagittal crest that give the robust Australopithecus skull its well-known appearance have been described, then examined for insights into the diet and behavior of these species. Although there is evidence for some hard food eating habits in robust Australopithecines, it is more likely that these species ate hard foods only when more desirable food was not available, and that they generally subsisted on large quantities of low quality food that had to be processed by intense mastication, although there was likely some variation in interspecific diets.