Magnumtergalis n. gen. a new genus from the Inter-Andean Valleys and midlands of the Colombian Andes’ central cordillera is described. Two very peculiar species are placed within this genus, M. aldarioarenasi n. sp. (type species) and M. albonigra n. comb. An unusual terminalia to the family Gryllacrididae characterizes this genus, in which the ninth tergite is noticeably prolonged, covering the other structures of the male terminalia. This is the first genus of leaf-rolling crickets described from the Neotropics in the last 80 years.