Didelphis marsupialis, type species of the genus Didelphis, is a widely distributed and commonly studied American marsupial. Unfortunately, the previously noncontroversial application of the epithet marsupialisLinnaeus, 1758, has recently been called into question, and the lectotype is no longer extant. To preserve long-standing binomial usage for this species and other congeneric taxa, we designate a specimen from Surinam in the Royal Ontario Museum as neotype.