Pewsey Downs (grid reference SU113636) is a 305.3 hectare biological Site of Special Scientific Interest on the southern edge of the Marlborough Downs north of Pewsey in Wiltshire, notified in 1951. It includes the Pewsey Downs National Nature Reserve.
In 1859, the Reverent Alexander Irvine recorded the following species of plants on the Pewsey Downs; Cirsium acaule; Carduus nutans; Cirsium eriophorum; Draba verna; Bunium bulbocastanum; Spiraea filipendula; Medicago sativa; Onobrychis sativa; Cichorium intybus; Campanula glomerata; Campanula rotundifolia; Asperula cynanchica; Polygala vulgaris; Saxifraga granulata; Anacamptis morio; Dactylorhiza maculata; Gymnadenia conopsea; and Botrychium lunaria.