Steinernema yirgalemense, a new species based on morphological and molecular data, is described from Yirgalem, Ethiopia. This nematode belongs to the 'bicornutum-group' which includes nematodes with horn-like structures in the labial region of the infective juvenile. The new species can be recognised by the infective juvenile having a body length of 635 (578-693) mu m, distance from anterior and to excretory pore of 51 (45-59) mu m; tail length of 62 (57-67) mu m and E% (EP/tail length x 100) of 83 (67-90). The lateral field pattern is variable from anterior to posterior; the formula for the arrangement of ridges from head to tail being: 2, 6, 8, 6, 2. The new species can be further recognised by male characters: spicule with large velum and tapering posteriorly to a point, the ratio SW (spicule length/cloacal body diameter) and GS (gubernaculum length/spicule length) and especially by the presence of 12 pairs of genital papillae plus a single midventral papilla. The 12(th) pair, located at the edge of the cloacal aperture, is an important character. The presence of a low epiptygma is another diagnostic character of the new species. The new species is a sister taxon to S. abbasi and is characterised by the sequence length of the ITS regions (960 bp), ITS 1 (270 bp), ITS2 (284 bp) and also by the pairwise distance of both ITS and D2/D3 regions between species of nematodes in the 'bicornutum-group'.