Sir William Douglas "le Hardi" (the Bold), Lord of Douglas (born after 1243 – c. 1298) was a Scottish nobleman and warlord.
William Douglas was the son of William Longleg, Lord of Douglas and it is supposed by his possible second wife, Constance of Fawdon. He first is recorded at an Assize at Newcastle-upon-Tyne in 1256, when his father made over a Carucate of land at Warndon, Northumberland to him. Douglas' father William Longleg was Lord of Fawdon, and had as his superior Gilbert de Umfraville, Earl of Angus, Longleg was acquitted of withholding rents by a jury, Umfraville notwithstanding attacked Fawdon, imprisoned Longleg at Harbottle Castle and made off with some £100 sterling of goods. William Douglas was injured in the fight. Ita quod fere amputaverunt caput ejus – So as to nearly cut off his head.
Sir William Fraser puts forward a theory that David Hume of Godscroft is mistaken about the William Douglas that went Crusading, and suggests that it is this William Douglas, the son the rather than the father, who accompanied David I Strathbogie, Earl of Atholl, and other Scots nobility on the Eighth Crusade in 1270, as recorded by John of Fordun in his Chronica Gentis Scotorum..