First record of Eaton, 1881 (Ephemeroptera, Heptageniidae) from Thailand with description of a new species.

A new species of Heptageniidae, , is described based on larvae, subimagos, eggs, and COI data. The mayfly genus Eaton, 1881 is reported for the first time from Thailand. The larva of the new species can be distinguished from other known species by i) lamellae of gill I ca 1/4 of fibrilliform portion and ii) mandibles and basal segment of maxillary palp without dense setae on margin.