Abstract
Summary The genus Thalictrum L. in New Guinea is revised based on morphological evidence. Full descriptions of the genus and the four taxa recognised are given. Two species are recognised: Thalictrum papuanum , widespread across New Guinea, and a new species described here; T. umbraticola , endemic to west New Guinea. Two new varieties are described: Thalictrum papuanum var. acutisegmentum and T. papuanum var. laticarpellum. One new synonym of Thalictrum papuanum var. papuanum is established: T. papuanum var. oranjense . Keys to the taxa and distribution maps, as well as preliminary conservation assessments, are provided.