Results are presented of an odonatological survey of 23 localities in Thala Barivat District of Stung Treng Province, northern Cambodia, on July 26 – August 1, 2016. Most localities were situated in areas of open low deciduous dipterocarp forests on gravel soils, some at hillside areas of tall evergreen dipterocarp forest. The great Mekong River right bank was studied within 7 km downstream of its Nimith (Nimet, Khon Thai, Labak Koun, Khone Pha Pheng) Waterfall. In total, 55 species were found, of which 52 identified to species and three to genus. Two species, Gynacantha saltatrix Martin, 1909 and Macrogomphus matsukii Asahina, 1986, were recorded in Cambodia for the first time. Five obligatory lotic species were found at the Mekong River, namely Dysphaea gloriosa, Prodasineura coerulescens, Burmagomphus asahinai, Nychogomphus duaricus and Onychothemis testacea, including tenerals of P. coerulescens and B. asahinai. Most probably these species breed in the Mekong reach which is enriched with oxygen downstream of the great waterfall cascade
