Sheffield Castle was a castle in Sheffield, England, constructed at the confluence of the River Sheaf and the River Don, possibly on the site of a former Anglo-Saxon long house, and dominating the early town. A motte and bailey castle had been constructed on the site at some time in the century following the Norman Conquest of England in 1066. This was destroyed in the Second Barons' War. Construction of a second castle, this time in stone, began four years later in 1270.