The wasp genus Liosphex Townes 1977 is revised and twelve new species are described: Liosphex achuar sp. nov. (Costa Rica, Ecuador, Panama and Peru), L. atratus sp. nov. (Costa Rica and Mexico), L. boreus sp. nov. (Mexico, Kentucky and Mississippi, USA), L. bribri sp. nov. (Costa Rica, Panama and Peru), L. darien sp. nov. (Panama), L. guanabara sp. nov. (Brazil), L. guarani sp. nov. (Brazil and Argentina), L. longicornis sp. nov. (Costa Rica), L. maleku sp. nov. (Costa Rica and Mexico), L. micropterus sp. nov. (southern Brazil and Paraguay), L. quechua sp. nov. (Peru), and L. tupi sp. nov. (Brazil). The male of L. trichopleurum Townes, 1977 is described for the first time. A redescription of L. varius Townes, 1977, including new diagnostic characters, is provided since the original description was based on a heterogeneous type series of specimens from different species. The revision includes images of all fourteen species, illustrations of the main diagnostic characters, an identification key to species and distribution maps for all species.