Wansdyke (from Woden's Dyke) is a series of early medieval defensive linear earthworks in the West Country of England, consisting of a ditch and a running embankment from the ditch spoil, with the ditching facing north.

There are two main parts: an eastern dyke which runs between Savernake Forest, West Woods and Morgan's Hill in Wiltshire, and a western dyke which runs from Monkton Combe to the ancient hill fort of Maes Knoll in historic Somerset. Between these two dykes there is a middle section formed by the remains of the London to Bath Roman road. There is also some evidence in charters that it extended west from Maes Knoll to the coast of the Severn Estuary but this is uncertain. It may possibly define a post-Roman boundary.