The genus Leptomyxa (Amoebozoa, Tubulinea, Leptomyxida) includes both nonreticular and reticular amoebae. Some of them are able to alter the shape of the cell from monopodial to flattened. To date, this genus includes 13 valid species. However, most of the species have been described from Europe and Russia, while data on other geographic regions are almost absent. In this paper, we describe the first species of this genus, Leptomyxa xiamenii n. sp., isolated from China, namely from a pond on the campus of the Institute of Urban Environment in Xiamen. The morphology of the current isolate is similar to other non-reticular species of the genus Leptomyxa. Meanwhile, it is characterized by the variability of nucleolar material and has a remarkable floating form with thin pseudopodia. In old cultures of this species, some cells are covered with a loose envelope consisting of bacteria embedded in a slime, which has never been observed for other Leptomyxa species. The 18S rRNA gene sequence reliably differs L. xiamenii n. sp. from all other species of this genus.