The Hoo Peninsula is a peninsula in Kent, England, separating the estuaries of the rivers Thames and Medway. It is dominated by a line of chalk, clay and sand hills, surrounded by an extensive area of marshland composed of alluvial silt. The name Hoo is a Saxon word believed to mean 'spur of land' or refers to the 'distinct heel-shape of the ridge of hills' through Hoo. Hoo features in the Domesday Book. The peninsula is home to internationally and nationally protected wildlife sites as well as industrial facilities and energy industries.