Hyaenodon ("hyaena-toothed") is an extinct genus of Hyaenodonts, a group of Creodonts. Some species of this genus were amongst the largest terrestrial carnivorous mammals of their time, others were only of the size of a marten. Hyaenodon was one of the latest genera of the Hyaenodonts and is known from the Late Eocene to Early Miocene. Remains of many species are known from North America, Europe, Asia and Africa (In 1993 42 species were distinguished).
The average weight of adult or subadult H. horridus, the largest North American species, is estimated to about 40 kg and may not have exceeded 60 kg. H. gigas, the largest Hyaenodon species was much larger. H. crucians from the early Oligocene of North America is estimated to only 10 bis 25 kg. H. microdon and H. mustelinus from the late Eocene of North America were even smaller and weighed probably about 5 kg.