﻿AbstractPhyllodiaptomus(Phyllodiaptomus)parachristineaesp. nov., a new diaptomid copepod, was collected from 30 sites in the lower Mekong River Basin floodplain in northeastern Thailand and nine sites in Cambodia. The new species is the 13thspecies of the genus to have been recorded across Asia. It has a wide range of habitats, occurring in small to large, temporary to permanent water bodies, and it can be found at any time of the year. The morphology of the new species is most similar to that of the males ofP.(P.)christineae, having a comb on the antepenultimate segment on the right antennule, symmetrical caudal rami, a narrow hyaline lamella on the leftP5basis, a distal accessory spine on the rightP5Exp-2, and a single-lobedEnpon the rightP5. On the other hand, the males of the new species have second and third urosomites without hair-like setae on the ventral margin, a rounded distal margin of theP5intersclerite plate, a semi-circular lamella on the rightP5basis, a strong principal lateral spine inserted at the proximal 1/3 of the rightP5Exp-2, and a two-segmented leftP5Enp. Morphological differences among species in the subgenusPhyllodiaptomus(Phyllodiaptomus)as well as the distribution and habitats of the 13 species and two subspecies ofPhyllodiaptomusin Asia are discussed.