Cliffe Fort is a disused artillery fort built in the 1860s to guard the entrance to the Thames from seaborne attack.
Constructed during a period of tension with France, it stands on the south bank of the river at the entrance to Cliffe Creek in the Cliffe marshes on the Hoo Peninsula in North Kent, England.
Its location on marshy ground caused problems from the start and necessitated changes to its design after the structure begin to crack and subside during construction.
The fort was equipped with a variety of large-calibre artillery guns which were intended to support two other nearby Thamesside forts.