A new species of Lusius Tosquinet, 1903 (Hymenoptera: Ichneumonidae: Phaeogenini) is described from the northwestern Andes of Colombia, and additionally, the geographic distribution of Lusius ferrugineus Graf, 2000 is expanded to Bahia and Rio Grande do Sul states, Brazil. New comparative diagnoses, distribution maps, and an illustrated key to Neotropical species are also provided.