Allerthorpe Common is a Site of Special Scientific Interest (SSSI) and nature reserve in the East Riding of Yorkshire, England. It is located close to the town of Pocklington. The site, which was designated a SSSI in 1951, lies on river and lake sands, which were deposited during the last glacial period 12-10,000 years ago. The soils are acidic and a variety of habitats, including wet and dry heath, mire, grassland and woodland have formed.The drier areas are dominated by heather interspersed with cross-leaved heath and purple moor grass. In the wetter areas purple moor grass forms dense tussocks. Common cottongrass and marsh cinquefoil occur in the wet mire conditions.