Nine Barrow Down is an elongated hill forming the northern ridge of the Purbeck Hills on the Isle of Purbeck in Dorset, England. The chalk down is part of the extensive Southern England Chalk Formation. The eastern end of the ridge, which carries the highest point, is also sometimes known as Godlingston Hill. The col of the railway cutting at Harman's Cross means that it has sufficient relative height that it qualifies as a Marilyn.