Protomarctus is an extinct monospecific genus of the Borophaginae subfamily of canids native to North America. They lived during the Middle Miocene 16.0—13.6 Mya, existing for approximately 2.4 million years. It was an intermediate-size canid, and more predaceous than earlier borophagines. The first specimen was found in Thomson Quarry, Sheep Creek Formation, Nebraska in a Hemingfordian layer. Specimens have since been found in present-day Colorado, as far west as California and as far southwest as New Mexico. They were short-faced, heavy-jawed canines.