Impatiens tanintharyiensis Ruchisansakun, Suksathan & Saw-Lwin from the Tanintharyi region of Southern Myanmar is described and illustrated as a new species. The presence of connate lateral united petals and a four-locular ovary, as well as results of molecular phylogenetic analyses of nuclear ITS and plastid atpB-rbcL spacer DNA sequences, suggest that the new species is a member of Impatiens section Semeiocardium (Zoll.) S.X. Yu & Wei Wang. The new species is morphologically most similar to I. spectabilis Triboun & Suksathan, but can be distinguished by its asymmetric flowers, saccate-bucciniform lower sepal, and shorter, slightly incurved spur. Floral traits, including the presence of a large floral chamber with a wide entrance, are consistent with the bee-pollination syndrome in Impatiens. Since I. tanintharyiensis is only known from two small populations, its conservation status is assessed as Endangered.

Three new species of Impatiens (Balsaminaceae) from Myanmar are here described: I. decurva Ruchis. & S.B. Janssens, I. hartnolliae Hook. f. ex Ruchis. & Suksathan, and I. oblongata Ruchis. &Van der Niet. The 5-lobed short fusiform fruit of all three species suggests that they are members of subgen. Impatiens sect. Uniflorae Hook. f. & Thomson. For I. decurva and I. oblongata, subgenus membership was corroborated by phylogenetic analyses of a combined dataset of nuclear ITS and plastid atpB-rbcL intergenic spacer DNA sequences. This was not possible for I. hartnolliae, which is only known from a single herbarium specimen.