A new species of theraphosid spider, of the genus Poecilotheria is described from southern India. Although having been collected previously and noted on three occasions in the historical record, the spider was erroneously thought to be P. fasciata (Latreille, 1804) from the island of Sri Lanka. The new spider, Poecilotheria hanumavilasumica sp. n. is named after the holy site on which it was found and can be readily distinguished from P. fasciata by the unbroken black band on the ventral surface of femur IV, the pale colour of the basal half of the metatarsus and the beautiful lilac/violet bloom that is the dominant colour of the ventral surfaces of the posterior legs. In P. fasciata, the black band is broken, the metatarsus dark and the dominant colour of the rear legs is a cold blue grey. Poecilotheria hanumavilasumica is thought to have a fragmented distribution in the south-east corner of Southern India – a range that in the past, probably extended south of Madurai and westwards to the foothills of the Western Ghats and the Agastya Malai range. The area, due to improved irrigation, is coming under increasing pressure from rice cultivation and initial surveys would indicate that, although threatened, a handful of functioning colonies precariously survive in the Ramanad desert region. Agriculture in this region was historically limited to subsistence farming and coconut plantations, but proposed Government irrigation projects now threaten this fragile equilibrium and raise the question – is it feasible to establish the largest colony, at the Hanumavilasum Temple site as a Tiger Spider Sanctuary? The spider has a historical presence on Rameswaram Island and the Adam Bridge causeway and it is plausible that it may be found in the war torn northern region of Sri Lanka – where no collecting has been undertaken for decades.