A new genus, Helenanomalon gen. n., of the ichneumonid subfamily Anomaloninae is described for two newly described species, Helenanomalon ashmolei sp. n. and H. bonapartei sp. n. Helenanomalon species are endemic to the remote South Atlantic island of St Helena, where they are the only known anomalonines. Unusually amongst anomalonines, there seems to be pronounced sexual dimorphism. The possible affinities of Helenanomalon are discussed.