Ratcliffe Mound is a Native American archaeological site in southeastern Ohio, east of Londonderry, where a solitary circular conical earthwork rises about 14 feet high and 86 feet across in open farm country near a stream. Although the region contains many Woodland-period mounds and both the Adena and Hopewell built earthworks nearby, this mound cannot be confidently linked to either culture because it lacks the diagnostic features and artifacts archaeologists would need. Its unusual setting adds to the uncertainty. Never excavated, Ratcliffe Mound remains a potentially valuable site for future research and was recognized for its significance by listing on the National Register of Historic Places in 1975.