Background <p>Ceratopogonid midges of the genus <i>Forcipomyia</i> (subgenus <i>Lasiohelea</i>) are small hematophagous insects widely distributed across tropical regions. In Australia, developmental stages of <i>Leishmania</i> (<i>Mundinia</i>) <i>macropodum</i> have been observed in <i>Forcipomyia</i> (<i>Lasiohelea</i>), suggesting that biting midges may play a role in <i>Leishmania</i> transmission beyond traditional sand fly vectors. However, in Southeast Asia—where leishmaniasis caused by <i>Mundinia</i> species is an emerging autochthonous disease in humans—fundamental information on <i>Forcipomyia</i> (<i>Lasiohelea</i>) diversity and its association with <i>Leishmania</i> remains limited.</p> Methods <p>An integrated morphological-molecular approach was employed to characterize <i>Forcipomyia</i> (<i>Lasiohelea</i>) midges collected using sweep nets from a leishmaniasis-endemic area in Nakhon Si Thammarat Province, Southern Thailand, near the residence of a patient with locally acquired cutaneous leishmaniasis, during January and June 2025. Morphological examination of mandibular dentition, sensory pits, cibarial armature, and spermathecal structure was combined with mitochondrial <i>cox</i>1 barcoding, Bayesian and maximum likelihood phylogenetic analyses, and species delimitation methods (ASAP and mPTP). Because females of the subgenus <i>Lasiohelea</i> possess a single spermatheca, only single-spermatheca females were selected for species identification. Specimens identified as <i>Lasiohelea</i> were subsequently screened for <i>Leishmania</i> using 18S rRNA-qPCR and ITS1-PCR, followed by nanopore-based ITS1 metabarcoding for species-level identification. Vertebrate blood meal sources were also characterized using vertebrate <i>cox</i>1 metabarcoding.</p> Results <p>From 264 collected midges, 72 female specimens with a single spermatheca were selected for analysis. Integrated morphological and molecular data identified seven <i>Lasiohelea</i> specimens forming four genetic clusters, comprising <i>F.</i> (<i>L.</i>) <i>parvitas</i> (<i>n</i> = 2) and three lineages closely related to <i>F.</i> (<i>L.</i>) <i>peditata</i> (<i>n</i> = 2), <i>F.</i> (<i>L.</i>) <i>humilavolita</i> (<i>n</i> = 2), and <i>F.</i> (<i>L.</i>) <i>taiwana</i> (<i>n</i> = 1). These were clearly separated from non-<i>Lasiohelea</i> taxa, including <i>F.</i> (<i>Euprojoannisia</i>) <i>fuscimana</i> and two unclassified Ceratopogonidae lineages. Phylogenetic and species delimitation analyses revealed cryptic genetic&#xa0;diversity despite morphological similarity. <i>Leishmania</i> DNA was detected in six of seven <i>Lasiohelea</i> specimens. Nanopore ITS1 metabarcoding identified autochthonous species (<i>L.</i> (<i>Mundinia</i>) <i>martiniquensis</i>&#xa0;and&#xa0;<i>L.</i> (<i>M.</i>) <i>orientalis</i>) and additional <i>Leishmania</i>&#xa0;species (<i>L.</i> (<i>Leishmania</i>) <i>amazonensis</i>&#xa0;and&#xa0;<i>L.</i> (<i>L.</i>) <i>major</i>), including mixed-species detections in four specimens. A single engorged specimen contained DNA from red junglefowl (<i>Gallus gallus spadiceus</i>).</p> Conclusions <p>This study provides the first integrated characterization of <i>Forcipomyia</i> (<i>Lasiohelea</i>) diversity and associated <i>Leishmania</i> detection in Southeast Asia. The results identified several putatively distinct species&#xa0;within <i>Lasiohelea</i> and provide evidence of natural exposure of these midges to multiple <i>Leishmania</i> species, suggesting a complex parasite-midge association and&#xa0;parasite co-circulation in the local environment. Although vector competence was not assessed, these findings suggest that <i>Forcipomyia</i> (<i>Lasiohelea</i>) may be involved in the circulation of <i>Leishmania</i> parasites and may represent promising candidates for further investigation of vector competence. Future studies focusing on host associations, parasite development, and experimental transmission are needed to clarify their epidemiological significance.</p> Graphical Abstract <p></p>