We report on a new genus and species of helohyid, Heliosus apophis from the middle Eocene Washakie Formation lower Adobe Town Member of Wyoming, which is recognized as latest Bridgerian in age (upper Bridger D/ Twinbuttean Biozone), with an estimated age of 47 Ma. The holotype consists of a left dentary with P4-M3 and an associated humerus. Body mass equations using humeral measurements indicate a large body between 232 to 706 kg, with a smaller estimated body mass based on dental remains between 45-64.6 kg, similar to extant wild pigs. The left dentary features bunodont teeth and lacks distinct paraconid cusps on the lower molars. The holotype is larger than Helohyus, including the largest species Helohyus lentus, but about half the size of Achaenodon from the Uinta Formation of Utah. The holotype is comparable in size to Parahyus vagus, but differs in the following features: it lacks distinct paraconids on the lower molars, it has a more reduced P4, and it has a narrower hypoconulid heel on the M3. Heliosus apophis is important because it establishes an early presence of large artiodactyls in North America during the Middle Eocene.