The Treaty of Wedmore or Treaty of Chippenham, signed at Wedmore in Somerset, was the result of the Battle of Edington (OE. Ethandun) in 878 AD, in which Alfred the Great defeated the viking forces of the Dane, Guthrum.

Effectively, the Treaty established and set the boundaries of the geographical area of Britain which was to be controlled by the Danes, the Danelaw. Under the terms of the Treaty, the Danes were obliged to give up areas of Wessex which they had occupied and to withdraw to a line north and east of Watling Street, the old Roman road.