During field work on mutualisms between oil bees and Cucurbitaceae in Yunnan, China, we discovered a new species of Thladiantha that we here describe and illustrate. It is overall similar to T. globicarpa A.M.Lu & Zhi Y.Zhang from Guangxi, but differs in the shape of its fruits. DNA sequences of the new species analyzed in the context of a densely sampled phylogeny of Thladiantha confirm its distinctness from all other species. The molecular data also revealed another collection of the new species made in Guangxi in 1937. Like all Thladiantha, the new species offers oil in glandular hairs on its petals and is pollinated by oil-collecting Ctenoplectra bees.