Risley Moss is an area of peat bog situated near Birchwood in Warrington, England. It is a Site of Special Scientific Interest and a Local Nature Reserve. It covers an area of 210.5 acres (85.2 ha) and is one of the last remaining fragments of the raised bogs that once covered large areas of South Lancashire and North Cheshire. Natural depressions in the glacial drift left by the ice sheets which covered the Cheshire–Shropshire plain during the last ice age, 10,000–15,000 years ago, filled with water, forming the meres and mosses characteristic of the area today.