High Halstow is a village and civil parish on the Hoo Peninsula in the unitary authority of Medway in South East England. It was, until 1998, administratively part of Kent and is still ceremonially associated via the Lieutenancies Act. The parish had a population of 1,781 according to the 2001 census, increasing to 1,807 at the 2011 census.

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.