Abstract
A new species of Pinnularia is described from a stream from Sikkim, India, falls under Eastern Himalayas biodiversity hotspot. Features that help make this species distinctive include having triundulate margin, a broad, central fascia, a central depression, and oppositely-deflected external distal raphe fissures. Pinnularia sikkimensis sp. nov. is compared with its morphologically similar species, such as Pinnularia nodosa, P. biceps, P. grunowii, P. septentrionalis, P. graciloides var. jogensis and P. ferrophila. The taxon is also recorded from two stream sites in Vietnam suggesting a wide distribution across Southeast Asia. In addition to the description of the new species, a checklist of endemic Pinnularia taxa from India is also presented.