Fort Darnet and Hoo Fort are nineteenth-century military installations on the River Medway near Hoo Marina. They formed part of the defences of Chatham Naval Dockyard and building of the forts was completed in 1871. They were originally designed for two tiers of guns mounted in a circle, with a boom barrier strung between them.
The forts were never used in anger, and were decommissioned before the First World War. In the Second World War the forts were used as observation posts, with platforms and pillboxes built on top.