A new species, Cleistanthus nokrensis (Euphorbiaceae), was collected and described from Indian Himalaya. This species is confined to the Nokrek Biosphere Reserve where it grows on the calcareous habitat in karst topography. On the basis of the critical features of its habitat, branches, petioles, leaves, and fruits, the species is compared with the closely related allied species, C. tonkinensis Jabl. and C. balakrishnanii Chakrab. Notes on its taxonomic description, photographs, ecology, associated species, population data, and threat perspective as per latest IUCN conservation status are provided. A key to the other taxa in the genus reported from India is provided for the first time, along with their distributional records and endemism.