Pevensey Castle is a medieval castle and former Roman Saxon Shore fort at Pevensey

Pevensey Castle is a medieval castle and former Roman Saxon Shore fort at Pevensey in the English county of East Sussex. The site is a Scheduled Monument in the care of English Heritage and is open to visitors. Built around 290 AD and known to the Romans as Anderitum, the fort appears to have been the base for a fleet called the Classis Anderidaensis. The reasons for its construction are unclear; long thought to have been part of a Roman defensive system to guard the British and Gallic coasts against Saxon pirates, it has more recently been suggested that Anderitum and the other Saxon Shore forts were built by a usurper in an ultimately unsuccessful attempt to prevent Rome from reimposing its control over Britain.

Anderitum fell into ruin following the end of the Roman occupation but was reoccupied in 1066 by the Normans, for whom it became a key strategic bulwark. A stone keep and fortification was built within the Roman walls and faced several sieges. Although its garrison was twice starved into surrender, it was never successfully stormed. The castle was occupied more or less continuously until the 16th century, apart from a possible break in the early 13th century when it was slighted. It had been abandoned again by the late 16th century and remained a crumbling, partly overgrown ruin until it was acquired by the state in 1925.

Pevensey Castle was reoccupied between 1940 and 1945, during the Second World War, when it was garrisoned by units from the Home Guard, the British and Canadian armies and the United States Army Air Corps. Machine-gun posts were built into the Roman and Norman walls to control the flat land around Pevensey and guard against the threat of a German invasion. They were left in place after the war and can still be seen today.