The Ouse Washes are an area in the Fens of Cambridgeshire, England. They cover the area between two tributaries of the River Great Ouse: the Old Bedford River and the New Bedford River (also known as the Hundred Foot Drain).

In 1630, Charles I of England granted a drainage charter to the 4th Earl of Bedford who engaged the Dutch engineer Cornelius Vermuyden to construct the two Bedford rivers. The area between the rivers is 20 miles long and almost 1 mile wide and acts as washland, i.e. a floodplain during the winter and, increasingly, also in summer.

The Washes are now of international imnportance for their wildfowl.