Nanium Townes, 1967 is a small New World parasitoid wasp genus in the subfamily Ctenopelmatinae Förster, 1869 (Hymenoptera: Ichneumonidae). Previously, it comprised five species: one from North America and four from Costa Rica. The current study reviews the Neotropical species of the genus, and includes descriptions of two new species, N. medianum Reshchikov & Sääksjärvi sp. nov. from Ecuador and N. atitlanensis Reshchikov & Sääksjärvi sp. nov. from Guatemala. A key to the species is provided.