The ruins of Donnington Castle stand on a high hill overlooking Newbury and the Lambourn Valley in West Berkshire. The only significant part of the 14th century fortification remaining is the gatehouse, with its twin conical towers bearing the damage inflicted by cannon fire during Civil War sieges. Between 1644 and 1646 the Royalist stronghold was attacked numerous times during an 18-month long siege, twice being relieved by King Charles I, in person. After the war it was largely demolished on the orders of Parliament.

Its most famous owner was Thomas Chaucer, son of the poet Geoffrey Chaucer, who held the castle in the early 15th century before it passed to the crown. Several monarchs are known to have visited, including Henry VIII, King Edward VI and Elizabeth I.

In 1946, when the ruins came under state ownership, the external walls of the castle were rebuilt to a height of 0.5 metres (2 feet) to indicate the original layout. Today it is Grade I historic building managed by English Heritage.