Lancaster Castle is a medieval castle and former prison in Lancaster in the English county of Lancashire. Its early history is unclear, but it may have been founded in the 11th century on the site of a Roman fort overlooking a crossing of the River Lune. In 1164 the Honour of Lancaster, including the castle, came under royal control. In 1322 and 1389 the Scots invaded England, progressing as far as Lancaster and damaging the castle. It was not to see military action again until the English Civil War. The castle was first used as a prison in 1196 although this aspect became more important during the English Civil War. The castle buildings are owned by the British sovereign as Duke of Lancaster; part of the structure is used to host sittings of the Crown Court.
Until 2011 the majority of the buildings were leased to the Ministry of Justice as HM Prison Lancaster, after which the castle was returned to the Duchy's management. The castle is now open to the public seven days a week and is undergoing a large-scale refurbishment. There is a large sweeping public piazza, allowing access to the cloistered area, renovated in 2019. A new section of the café has been built, against the old outer curtain wall, which was reduced in height to afford views of the neighbouring Lancaster Priory. This is the first 21st-century addition to the castle. Another renovated building adjoining the café is leased to Lancaster University as a campus in the city with small conference facilities.
