Eucosmodon is a genus of extinct mammal from the Paleocene of North America. It is a member of the extinct order of Multituberculata within the suborder of Cimolodonta, and the family Eucosmodontidae. This genus has partly also been known as Neoplagiaulax. All known fossils of this small mammal are restricted to teeth.

All known species of Eucosmodon have been found in the San Juan Basin of New Mexico (United States).