Abstract
Clerodendrum angustipetalum (Lamiaceae), an endemic species to Narathiwat province, southern Thailand, is described and illustrated as a species new to science. It is similar to C. nutans in having an elongate pendulous inflorescence, but essentially differs in the thicker leaf texture (subcoriaceous vs membranaceous), the calyx tube being almost twice as long and the corolla lobes being half as broad. In addition, the new species has longer calyx lobes, corolla lobes and stamens. The conservation status of this species is assessed as Critically Endangered (CR, B2a + b(ii, iii)+C2ai+D) due to being known from a single locality with a small population of less than 50 individuals. A morphological comparison between similar species and an updated key to Clerodendrum species with pendulous inflorescences from southern Thailand is also presented.