Hattomys, a new genus of Cricetidae, is described and three new species H. beetsi, H. nazarii and H. gargantua are attributed to it. Hattomys are very large cricetids, and the evolution of the genus is characterized by a considerable increase in size, and an increasing predominance of ridges over cusps. The supposedly oldest Gargano localities yielded, apart from the lineage H. beetsi-nazarii-gargantua, some scarce material of three other hamster species: a Megacricetodon, a Cricetulodon and a Cricetus. Comparison with the Spanish sequences of rodent faunas shows that the Gargano faunas probably are of late Turolian age, equivalent of the Messinian.