Westerham is a town and civil parish in the Sevenoaks District of Kent, England. It is located 3.4 miles east of Oxted and 6 miles west of Sevenoaks, adjacent to the Kent border with both Greater London and Surrey. It is recorded as early as the 9th century, and was mentioned in the Domesday Book of 1086 in a Norman form, Oistreham. Hām is Old English for a village or homestead, and so Westerham means a westerly homestead. The River Darent flows through the town, and formerly powered three watermills. The total population in 2021 was 4,498.