Previously known only from isolated teeth and lower jaw fragments recovered from the Cretaceous and Palaeogene of the Southern Hemisphere, the Gondwanatheria constitute the most poorly known of all major maminaliaform radiations. Here we report the discovery of the first skull material of a gondwanatberian, a complete and well-preserved cranium from Upper Cretaceous strata in Madagascar car that we assign to a new genus and species. Phylogenetc analysis strongly supports its placement within Gondwanatheria, which are recognized a monophyletic and closely related to multituber-culates an evolutionarily success clade of Mesozoic mammals known almost exclusively from the Northern Hemisphere. The new taxon is the largest known mammaliaform from the Mesozoic of Gondwana. Its craniofacial anatomy reveals that it was herbivorous, a us in, large-eyed. of and agile, with well-developed high-frequency hearing and a keen sense of smell. The cranium exhibits primitive and derived features, the disparity of which is extreme and probably reflective of a long evolutionary history in geographic isolation.