Of the 116 mammal species present in the Greater Antilles at the start of the Holocene Epoch, only 56 now survive, with more extensive species losses (∼80%) in native lineages of sloths, shrews, rodents, and primates than in bats (∼25%). Native species occurrences and extinctions are summarized herein for Cuba, Hispaniola, Jamaica, and Puerto Rico and used to introduce this Journal of Mammalogy Special Feature on insular Caribbean mammals. Recent efforts to understand extinct and extant Caribbean mammal diversity highlight the utility of paleobiological perspectives for exposing the trajectory of species losses and informing how best to protect remaining biodiversity in this region.