Alnwick Castle (/ˈænɪk/ (listen)) is a castle and country house in Alnwick in the English county of Northumberland. It is the seat of The 12th Duke of Northumberland, built following the Norman conquest and renovated and remodelled a number of times. It is a Grade I listed building and as of 2012 received over 800,000 visitors per year when combined with adjacent attraction The Alnwick Garden.
Alnwick Castle guards a road crossing the River Aln. Yves de Vescy, Baron of Alnwick, erected the first parts of the castle in about 1096. Beatrix de Vesci, daughter of Yves de Vescy married Eustace Fitz John, Constable of Chestershire and Knaresborough. By his marriage to Beatrix de Vesci he gained the Baronies of Malton and Alnwick. The castle was first mentioned in 1136 when it was captured by King David I of Scotland. At this point it was described as "very strong". It was besieged in 1172 and again in 1174 by William the Lion, King of Scotland and William was captured outside the walls during the Battle of Alnwick. Eustace de Vesci, lord of Alnwick, was accused of plotting with Robert Fitzwalter against King John in 1212. In response, John ordered the demolition of Alnwick Castle and Baynard's Castle (the latter was Fitzwalter's stronghold), but his instructions were not carried out at Alnwick.