Hoplophoneus (Greek: "murder" (phonos), "weapon" (hoplo)[1]) is an extinct genus of the family Nimravidae, endemic to North America during the Late Eocene to Early Oligocene epochs (35–29 mya), existing for approximately 6 million years.

The largest known specimen is estimated to have weighed 160 kg (350 lb), similar to a large jaguar.

The larger H. sicarius and H. mentalis had very large upper canines and a massive flange at the front of the lower jaw.

[5] An adult specimen of Hoplophoneus discovered in Badlands National Park, South Dakota, in 2010 by paleontologist Clint Boyd et al. was found to have bite marks on its skull from the teeth of another adult individual of Hoplophoneus.

Similar finds also reveal that such fights were likely commonplace among nimravids and that they would often aim for the back of the skulls and eyes of their opponents.