A new and distinctive species, Pilea nguruensis Friis & I. Darbysh. (Urticaceae), is described based on material collected in 2006 from moist montane forest in the Nguru South Forest Reserve, Nguru Mountains, central Tanzania, and its conservation status is assessed. The paper supplements a revision of the African species of Pilea Lindl. made by Friis in 1989, and accounts of Pilea for a range of other African floras including the Flora of Tropical East Africa.