Prionessus is a genus of extinct mammal from the Paleocene of Central Asia. It was a member of the extinct order Multituberculata within the suborder Cimolodonta and superfamily Taeniolabidoidea. The genus was named by Matthew W.D. and Granger W. in 1925 and is based on a single species. The species Prionessus lucifer was named by Matthew W.D. and Granger W. in 1925. Fossil remains have been found in the Upper Paleocene strata of Gashato, Naran and Nomogen in Bayan Ulan of Mongolia and China.