A new species of Boraginaceae, Onosma lhokaensis, is described and illustrated from Xizang, China. The new species closely resembles O. waddellii and O. waltonii in having azure corollas, coherent anthers and glabrous filaments, but differs in having particularly bristly indumentum, observably narrow corolla, longer calyxes and anthers, and remarkable nutlets with stipitate cicatrix. An updated key to the species of Onosma from Xizang is also provided.