Protoceras was named by Marsh (1891). Its type is Protoceras celer. It is the genus of Protoceratidae and subfamily Protoceratinae. It was assigned to Protoceratidae by Marsh (1891) and Carroll (1988); and to Protoceratinae by Matthew (1908), Webb (1981), Prothero (1998), Webb et al. (2003) and Prothero and Ludtke (2007).