Hemicycliophora ahvasiensis n. sp., recovered from the rhizospheric soil of date palm in Khuzestan province, southwest Iran, is described and illustrated based upon morphological, morphometric and molecular data. The new species is characterized by its sheath, closely fitting most of the body, cuticle with or without numerous irregular lines, sometimes appearing as blocks in distal body region. Lateral field without discrete longitudinal lines, but often with continuous broken striae or anastomoses. Continuous lip region with single annulus, slightly elevated labial disc, stylet with posteriorly sloping knobs. Vulva with or without slightly modified lips, spermatheca with sperm and tail conoid, symmetrically narrowing at distal region to form a narrow conical region. Morphologically, the new species looks similar to H. indica, H. labiata, H. siddiqii, H. tenuistriata and H. typica. The latter species appears more similar to the new species under light microscopy, but could be separated using the scanning electron microscopy and molecular data. The new species was also compared with H. epicharoides and H. dulli, two species with close phylogenetic affinities to it. The phylogenetic relationships of the new species were reconstructed and discussed using partial sequences of the D2-D3 expansion segments of large subunit, and internal transcribed spacer regions (LSU D2-D3 and ITS rDNA). Hemicycliophora conida, the second studied species, was recovered from north Iran and characterized by morphological and molecular data.
